If the choice is only between Boma and Tutto, I'd pick Boma based on the menu. I'm a little too picky for Tutto and they don't really have much of anything that I like that would make sense on the dining plan.
However, if it were up to me to spend all 6?
1) Sanaa
2) Boma
3) San Angel Inn
4) Kona Cafe (Though, if I were into 'Ohana, I'd put it here, again that pickyness strikes back!)
5) Mama Melrose (hey, it's simple, but I like it, and I'm the one making the choices for my list

, besides, the list needed a DHS day meal) - 50s would also work if you're into that type of thing
6) Crystal Palace (guess I should include a MK meal... this is the best bet on
DDP and has been the better of the character meals that I've had)
For Le Cellier, it's not worth 2 credits on DDP at all. DxDDP is debatable, but for normal DDP it's not worth it. I haven't had a bad meal there (out of the 3 or 4 I've done), but the way the math works out and the lack of it really being anything special just doesn't fit with DDP at all.