It largely depends on the dog in my opinion. MOST dogs can easily be motivated by food, but there are the few who are happy to eat....but don't care much about being rewarded with it. For instance, I have known some dogs did not do well with treat-training, but excelled when switched to praise training. Some dogs are simply extremely eager to please, and would much rather receive a "Good dog" and an ear rub than a piece of kibble. My Rottie mix did not do well at all with treat training, but learned exceptionally well with praise training. He wanted to make me happy, and he really liked to learn. He pays attention better than some other dogs that I have treat trained. Mud learned some tricks with only praise, and some tricks with treats and praise. We eventually get off the treats and go to just praise or play. She does well with both, and loves to learn and succeed.
As far as dogs only performing for treats, I think this depends on the trainer. I have seen it in many dogs...for instance, the trainer presented the treat to the dog before each trick, then lured them into the position and they were rewarded. The dog actually learned the trick in the presence of a treat, but not in the absence of it as the trainer never taught the dog anything without it. The dog became trained to do things on cue in the presence of the treat. If the treat was not first presented to the dog, the dog did not realize that it was supposed to carry out the same behavior. Of course, this can quite easily be fixed, but it never would have been a problem had the trainer used either clicker training or simply didn't bring out a treat, almost flaunting it to the dog, then lure into position, then reward.
For an extremely easily distracted dog, I would suggest treat training. This will help the dog learn to focus on the the handler, and become more willing to learn and do things not only for you but also for himself. For a dog that thrives on praise, I think you can go either way. The form of training you use depends a lot on each individual dog, to me.
The difference between the treat "flaunting" and training that usually results in an obedient dog in the absence of treats is this: look carefully at the videos in DTA's classroom. Jean holds the treat in his hand, concealed although the dog knows it's there. Then he lures the dog into whatever position, clicks, and rewards. The dog associates the click as a positive sound which results in food 9 times out of ten. The trainers that I have seen with a food-only obedient dog held the treat, maybe even let the dog nibble it, then lured into position and rewarded. The dog was actually rewarded in some way before earning the reward. Without the "encouragement" beforehand, he is not aware that he is supposed to perform the same behavior without this.
Like CollieMan, my dogs have to wait before leaving for a walk or just outdoor play. Their reward is play, exercise, and just fun in general.