Dao
No longer a newbie, moving up!
1. What would you guys personally get if you had to choose between the Nikon D90 and the Cannon 50d? Remember I'm looking to do portraits, headshots, and modeling portfolios....
From what I read and learned so far, Low Noise in High ISO factor may not be a major factor for you since you mainly do portraits, headshots and modeling portfolios. This type of photography generally need good lightning. In other words, you seldom need to crank up the ISO. Most of the time, you ISO setting will be 100 or 200.
As far as what camera or lens(es) to start with, it is highly related to your budget. For Nikon, I will for sure start with at least D80/D90 because of the focus motor issue with D40/D40x/D60. As for D90 vs 50D ... it is really a personal preference. Both are great camera.
I do found that some portrait photographers here prefer using a Full Frame camera.