Hi Pat,
Welcome aboard. That seems like an apples and oranges comparison to me. Besides the extra space in the 22, you have the ability to travel comfortably at speeds over 20 knots with the C-Dory vs displacement speeds with the R-21. They are both very capable boats, but especially with the consideration of long distance travel along the ICW, the CD-22 would give you more of everything: galley space, dinette, storage.
I have no doubt that folks who own an R-21 will chime in here and tell you how they use pints per hour vs the fuel burn of the C-Dory. Trying to get the comparisons similar, if you slow the CD-22 down to displacement speed, you should be somewhere on the high side of 6 mpg, and a fuel burn of less than 1 gallon per hour.
Don't get me wrong, I think the R-21 is a nifty little boat. My buddy Herb recently brought home a pre-EC version. It is stout, well-built, functional, and extremely cute. BUT, it just doesn't have the accommodations of a CD-22 for extended traveling. The lower coaming and the bigger cockpit are great for carrying people back there, but I personally prefer a smaller cockpit and taller topsides for traveling outside of protected water. Just a personal preference.
There are lots of us here who came from a sailing background. The best sailboats for open water sailing have the smaller cockpits to minimize a problem with getting pooped. And decent accommodations in the cabin to support the stores and comfort necessary for the trip.
The above is one guy's non-paid opinion and not the opinion of the C-Brats staff or management. Go to the TugNuts forum for a completely different opinion... and you will be directed to the story of the 3 guys who took their R-21s up the Inside Passage. Then come back here and read about how many C-Dory folks have made the same trip. You can make either boat work... it comes down to the big questions of space and performance that lead me to favor the 22 for the use you're suggesting.
Good luck with your decisions and keep us posted on your search.
Best wishes,
Jim B.