Downs Photography wrote in post #10533648
Personally I don't see anything wrong with the 550D. Unless you are shooting sports the 7D should not be a option. T2i and the 7D iq is the same. Now as far as the 5d mark II. Why do you feel you need it?
Great question. And when combined with the observations about the OP having a bunch of EF-S lenses, I'm having a hard time wrapping my mind around the OP's dilemma.
No offense intended, but I get the feeling this is another case (more clear than most, but still not in contention for the top 100) of someone thinking that buying a body will improve their skills (results) as a photographer.
I can't help but wonder how long the OP has been using an SLR. The 550 is a pretty new camera. The buyer should be aware that other than FPS, it's essentially going to deliver virtually identical images as the 7D. The 5D2 can't use the EF-S lenses at all, so they become useless (and some of the very few Canon lenses that won't hold a great deal of their value).
As to the question, if money is not an object, then the 5D would be more suitable (as per common wisdom) for portraits. But a skilled photographer can get great portraits with a crop camera. The potential for outstanding resolution with 18 or 21MP exists for both. Lens choice may compensate for the full frame vs. the crop sensor. But only as far as depth of field, which isn't the critical issue for portraits so many seem to think. Is having the subject's nose in focus and the ears out of focus a good thing? 
I'd put the sensor size a distant third (at best) behind the use of light and composition. Very distant. In real life, for a top notch portrait and for most subjects, a talented make-up artist will be the number one factor putting the equipment (and even the skill of the photographer - except for lighting) almost out of the equation.
Peace,
D.