20D+cheap superzoom vs ultrazoom P&S
I currently have a 20D with a std zoom (18-50 2.8), and am in need of a longer zoom as my kids start to get into sports (older one 4 yrs old starting to play soccer). I know an L telezoom will be a better solution than one of the P&S ultrazooms, but what I do not understand is where the break even point is. Will I get better results with the 20D and a cheap zoom (e.g. older 75-300 IS or non-IS)??? or do I need at least one of the newer 70-300IS lenses? I'm talking from an image quality and usability standpoint (e.g. focus accuracy/speed/tracking). I've seen used S2 IS for under $100, and the newer ultrazoom P&S are upwards of $300 (where I would probably just buy a nicer lens for the 20D). Most of my shooting will be in daylight (at least for a few years), so please advise on daylight performance differences.