Matt,
I don't think you'll notice any difference in ease of use between these cameras except for the following issues:
If you buy a webcam designed to sit on your computer and take images of your face you'll need to remove the lens and attach an adaptor that fits in your focuser. I think you'll need to purchase the adaptor from someone like Steven Mogg. If you buy a webcam that has been built for astro imaging the steps above will have been done for you but you'll pay for someone else to do this for you.
The software you get with each camera is going to be different. I bought a Neximage and it comes with Amcap which is very basic image capture software. I'm not familiar with the Phillips software but the screen shots I've seen lead me to believe it is similar in functionality to Amcap with some nicer features. In any case you can download K3CCD tools free and this is probably going to be better than whatever you get with either webcam.
I've recently purchased a DSI to get longer exposures but I'm still having fun with the Neximage.
I've seen some web sites that suggest that the Neximage is actually similar if not the same as the original Phillips Toucam internally. I'd be interested if anyone on the forum has managed to confirm this it true or false?
Here are two links that show how to do a long exposure modification for each camera. Both refer to the Phillips SAA8116 chip.
http://fdiazhome.tzo.com/Astronomy/Neximage-Mod/
http://www.burri-web.org/bm98/l3k/circuit-layout.htm
I've posted a few Neximage pics (as well as DSI pics) on this forum so if you want to get an idea of what to expect check out the forum search function.
good luck
Peter.