Starlet,
Bear in mind that a top handle saw has a lot better clearance for tight spaces while pruning. If this is a concern, it might be consideration. Bar length will affect this as well. You might only need a 12" bar or so, for the work described.
A smaller back handle saw is better on the ground than the tree, and a top-handle saw is better in the tree than the ground, especially for pruning, where you have to get into tight spaces without damaging nearby wood.
You'll be able to figure out which is a better starting point. As time goes on, you'll be able to pick-up the other choice from what you make now, and since you are looking at quality brands, you'll have a saw that will last though what you're putting it through.
I realize that this may seem a little strange, but a mock-up of the saws would allow you to get the feeling of the clearance they allow if you take them into the tree. Cardboard would be the easiest to work with, I think. Papier-mache could be fun if you can get someone to twist you up a balloon chainsaw or two.
You'll know best what will work for you as your initial saw purchase. As I was previously posting, I think a top handle will be more versatile, as the top-handle will not impede you on the ground, however you may have to bend a little more. Whereas the back-handle can make it harder to get the proper pruning cut positioning in the tree.