I agree with those above, if you smoke turkey, the best flavor comes from a whole turkey. I smoked just a turkey breast once, but the full flavor especially in the gravy just wasn't there. It did make great cold sliced turkey sandwiches though..
Bottom line is you have to make what appeals to you... Some like only light meat and the breast only would be fine for them.
Humphrey's DownEast Beast W/BBQ Guru