Sorry for the delayed reply, been out of town for a few days...dang, missed Fred's smart-a$$ reply...
RE tuners/chips/Ford Powerstrokes - all of my personal experience is with the 7.3. I have no first-hand knowledge on how well they work on the 6.0's, but from what I've read, I'd be more cautious using them on that engine, for a few reasons.
First, the 6.0 runs hotter than the 7.3, as many folks who have installed EGT gauges will testify. An EGT gauge and 4" exhaust update is a must in any case, but you may find yourself needing to keep your foot out of things when under load with a chipped 6.0.
Second, the stock 6.0 has significantly more HP/torque than a stock 7.3. I'd question the need for a chip for strictly power reasons; most reports I've read on the 6.0 indicate it does a fine job un-chipped.
Lastly, there have been numerous reports of Ford not honoring warranty claims on chipped 6.0's. I'm sure it all depends on the particular claim, i.e. what component failed, but unless one cares to be dishonest (by removing chips/programs prior to dealer visits), one needs to weigh the risk of a denied warranty repair. Even if the chip/program isn't responsible for a component failure, you could be in for a fight if Ford thinks otherwise - and their pockets are probably deeper than most of ours. I've read several accounts of folks being stuck with $7K+ repair bills that would have otherwise been honored had they not chipped their 6.0's.
The 7.3 is an entirely different story. First, most of them are out of warranty, or close to it. Second, they've been around much longer - the tuners and aftermarket companies have quite a bit more experience in safely increasing performance on them. Both of my 7.3's are chipped, and the difference is pretty amazing - not only from a power perspective, but from a driveability one as well - the chips typically modify shift points in addition to the big performance gains. As is the case with any chipped diesel, your tranny will take the brunt of the power increase. If you don't abuse your new-found power, the stock tranny will probably hold up fine. If you are "right-foot heavy", plan on about $3500 to make your tranny bullet-proof.
Based on my 7.3 experience, I'd go with a chip over a tuner. While more difficult to install, they offer several benefits. First, the programs just seem to be better; virtually everyone who has compared a tuner program to a chip will verify they get more power, with lower EGT's as compared to a tuner. Secondly, it's handy to have multiple programs; I have my daily driver program which is fairly aggressive, but I can switch back to a safer tow program at the flick of a switch.
Best site I've found for Ford Diesel info -
The Diesel Stop. Much more info has been written there than we'll ever address here. Best Ford diesel performance vendor I've dealt with is Jonathan at
Swamp Donkey - he's very knowledgeable and helpful, and has good pricing to boot.