depending on what you do the most. I personally would not purchase anything with a smaller chip capacity than a 12" capacity. that being said if I was to be doing lots of pruning and trimming, a bandit 200 model is nice and can take a small tree, but gets bogged down when chipping monster...
Make sure to have a plan like what JustinK said. Also make sure you do a tree risk assessment(sound the tree look for weak crotches and raised soil or root flares)before any climb. If you are going to use a chainsaw be sure that you are comfortable and always use 2 hands. Oh and be safe have fun...