easy.
go with the project mix.
you keep the option of pro tools open.
digidesign only supports digidesign or m-audio.
[you would need to pick up the m-powered edition of pt in order for the two to function properly together.]
i have plenty of experience with the project mix.
it's a great piece of equipment.
& you can use it brilliantly with a lot of programs, including even garageband.
never honestly used either tascam interfaces. tascam's a great manufacturer for the most part. but, digidesign doesn't support their interfaces.
so go with the project mix.
it keeps your options open.