Hi Tightline,
It helps to know the underlying principle behind the design of a hull or hull type. This is no different than deciding on a vehicle except that since we almost all grow up with cars and trucks as part of our daily lives we acquire a high degree of familiarity with them. That's typically not the case with boats and if it is then usually there aren't many questions to be asked unless we're venturing into a usage we're not familiar with.
When you shop for a vehicle you've got a pretty good idea of the broad category of vehicle you're looking for; family sedan, economy commuter, small pickup, heavy-duty pickup, sports car, etc. After that it's a matter of narrowing down the field within that category. For instance, it doesn't make much sense to most folks to compare a Mazda Miata and a 1-ton Dodge Dually pickup. You may be still trying to decide between the two but the decision there is really about which category of vehicle meets your needs not which specific vehicle does; at the point illustrated you've already decided on the Miata if you go with a sports car and the Dodge if you go with a pickup.
To put this in boat perspective...you can't make a direct comparison between the C-Dory 22 Cruiser and a Sea Sport, or Seaswirl, etc; they're in totally different categories. The CD22 is much like a Volkswagen Camper Bus; the other boats more like Sports Sedans (BMW's, Jaguars, etc). An Arima equates to a mini-van as does the modified-V (not deep-v) Parker. This is an oversimplification but for the sake of illustration it's correct.
It's all about hull shape and design. A deep-v hull, by definition, is a high performance hull just like a Corvette in the car world is a performance car; someone looking to haul kids and antiques around probably isn't looking at the Corvette (except for fun). Deep-v hulls were developed for offshore racing and patrol/rescue boats and they do their job superbly; however, just like a high performance car they require a lot of horsepower, they're not the best around town and when "at speed" they take a lot of attention from the operator. Get distracted at 30 knots sliding down the face of a wave with a deep-V and stuff it into the backside of the next wave and you'll have a personal definition of a broach (and hopefully not a roll). Kind of like not paying attention when you stuff a sports car into a corner at speed in the mountains.
There is absolutely nothing wrong with a deep v boat; they're lots of fun and they cut through rough water as well as any monohull is going to. For family use one of the most common complaints is that you can't slow down. Most of these hulls will not stay on plane much below 18-20 mph and when they come off plane the stern settles quickly (not much lift at low speed from the deep-v aft) so that visibility is sometimes an issue and the boat gets a "wallowing" feeling. At slower speeds (5 to 10 mph) they tend to s-turn as the sharp entry tacks first one way and then the other. Lift in these hulls depends on speed, speed takes horsepower and horsepower takes fuel; it's really that simple. As good as these boats are at getting out to the fishing grounds once there they tend to roll pretty badly; after a full day aboard you're usually pretty whipped. Even though at speed a deep-v hull will 'cut' the water and not necessary pound when the water goes up and down the boat has to go up and down; when you 'bottom out' after cutting a wave and change direction (with the bow lifting) your body has to deal with a lot of g-force and that flat wears a person out.
Then there's a whole slough of boats that fall into the "modified-v" range; this is an attempt to get some of the performance a deep-v but to eliminate the need for such a large engine and also to get a more stable boat when at rest or trolling. A modified-v can really go from almost a deep-v to something close to a flat bottom; it's such a wide range of designs that it's really a catch-all category for any hull that planes but isn't distinctly in another category (deep-v, dory, tri-hull, flat, etc). Typically a hull is considered deep-v when it's around 22-degrees (or more) at the transom.
Then you have the dory hulled boats; the C-Dory being the most common. These hulls are derived from workboats where seakeeping ability was more important than ultimate speed and the ability to carry a load was usually important. Another important aspect was economy of operation; that comes from a couple of things with the dory hull: one is that it's quite easily driven and with its almost flat stern planes easily and at relatively slow speeds and two, there is almost no transition to plane, meaning you can choose just about any speed and not have the bow rise, the boat wallow or the fuel economy head for the basement. This is particularly nice when the water conditions are rough; you can slow down to a pace that makes things more comfortable and less scary for your passengers. The hull is designed to have a small waterplane area when light so that it can run easily out to the work area; when loaded the hull gets pushed down further into the water and picks up stability. Because of the sloping sides the hull is able to handle very heavy loads. With the boat light (as most CD22's are compared to their workboat brethren) the initial stability of the boat is lower; that is, it tips quite easily but as soon as it does it starts to put more of the flaring sides in the water and picks up secondary stability very quickly. This is a good thing, the lower initial stability allows the boat to 'give' to a wave and dissipate some of the wave's energy so the occupants of the boat get a better ride. With the great secondary stability of a dory hull there's little chance of a wave upsetting (rolling) the boat since it gets very stiff the further it rolls; and because the hull initially rolls easily the wave can't do a 'pancake' flip kind of thing since the hull is already giving to the wave and absorbing some energy.
The trade-off on the dory hull is less space inside (since the sides slope in so much) and lower speeds in rough water. The smaller space (when compared to the same size deep-v or modified-v boat) in the dory hull shows up primarily at floor level (not typically a 'big deal'). And speed is all relative; when the water conditions get bad enough every (small) boat has to slow down, so the speed difference between the dory and faster hulls shapes drops signficantly. The big difference is that the dory hull is then in its element while the other hulls (the deep-v more so, the modifieds less) are not happy and operating out of there designed speed range.
And, being the vehicular based folks we are, we tend to over-emphasize the speed requirement in boats. We think nothing of a 200 mile day in our cars/trucks but in a boat that's a LONG trip. If we're going 20 miles in a boat the distance isn't great enough to make enough time difference to warrant the extra speed. In rough weather a C-Dory may be making 10 knots; there are very few small boats that will be making more than 20 knots in those conditions and most (even deep-v's) won't do that and at 15 knots they're trully uncomfortable. The real reason one wants a fast boat is for the fun of it since the math on paper doesn't work out for distance unless you're travelling further than most folks. If you're on a really long trip then the slower speed wears you out less and requires less stops (to rest and relax from being in a high speed boat); in the end the travel time difference is not as much as it first apprears. If you're doing speed specific things like water sports, bass fishing, etc then you already should be looking at the boats designed for that use. The argument that you need a fast boat to outrun the weather is a myth (perpetuated I think by the marketing folks at 'fast boat' companies); any storm worth running from is moving faster than any (small) boat I know of can run...especially in heavy seas. Discretion is the better part of valor; the best way to stay out of a storm is to not go out in one (listen to the weather forecasts). If you do get caught in heavy weather almost any decent boat will handle it a lot better than the crew will. Most sinkings are the result of water coming into the boat through man-made holes (failed thru-hulls, failed hoses, etc) or structural failures (which don't seem to happen on modern, quality-built boats) and not from water coming over the boat; ending up in the surf doesn't count and neither do bar crossings on bad days...as even the Coast Guard finds out the hard way on occasion.
I didn't mean for this to turn into a book...I do hope the information helps folks though. Best of luck on your quest for your perfect boat.
