Feeding costs will be more for a draft/draft cross than a lighter horse, but only if your draft is a big horse... some draft breeds are only around 15hh, and yes they eat more than a 15hh light breed, but do not eat more than a 17hh light horse.
As for the benefits and downfalls:
Draft breeds and especially draft crosses are not very expensive - which is great when you're buying, not so great when you're selling. Chances are if you buy 'em cheap, you won't make much of a profit when selling. For example, if you buy an untrained Warmblood for $5000 and train them up, you have a potential for profit, say if you get them showing 3' in shows and placing decently well, $20,000 is a reasonable price sticker.
But, if you buy an untrained Draft or Draft cross for $5000 (which is on the high side for an untrained Draft) and even if you get it to the same training level as a WB, I would expect around a $10,000 selling range.
Most Draft horses have very tough feet, and if they don't seem tender with light trail riding, I don't see any reason for them to be shod.
I hope I've helped!