This topic has been posted a bit already, but I want to tailor a more specific question to my needs.
I've got a nifty fifty (50mm f/1.8 cheapie) on my 50D crop body that I use for amateur portrait shoots, mainly children but sometimes families. However I've been doing a lot of mobile studio shoots lately in friends' homes but often there is not enough space in the house and I find myself backing up against the far wall just to fit a few heads into the frame. I do have a 18-200 EF-S but I'm reluctant to use this for shots where I want full clarity and ability to shoot wide open.
So I'm looking to widen my frame and am thinking about the next lens (full frame body is out of the budget for now and would prefer to spend on quality glass).
Should I go for a 35mm or a limited range zoom like a 24-70mm? Would the 24-70 be just as sharp (at the same focal length) as the 35mm prime? I'm really keen on the best clarity possible, given that I'm trying to capture children's faces and especially their eyes.
Obviously the 24-70 gives me some flexibility, so that's good, but if someone tells me that the 35mm is sharper, I might lean towards that. It's purely for portrait shots so will be a dedicated lens.