Hi people, While I was helping a friend searching for dslr, I came across Canon XS, XSi & Ti, xTi (if such model even existed). Are they just difference in terms of pixel size or they are intrinsically designed for different application? In your opinion, which one is the most optimized entry level camera long term wise so that she wont needing an upgrade very quickly. She own a daycare, so is mostly taking pictures of kids & the parents. She also loves taking outdoor pictures when go camping. I thought maybe she should search in craiglist to get a used 20D/30D/40D/50D, it is a better investment to get better quality pictures or maybe I dont know what I am talking about? As usual, thanks for your advise.