I like French doors - they look better imho, and have other advantages (easy operation, better weatherseal, wider opening, etc.) You can also have screens on them - we do - that either are extra doors that attach to the glass doors, or replace one of the glass panes in the french door itself.
That said, if you really need to go with a slider, I'd pick sliding doors that give you the widest opening possible.
-Ivy
Parenting two active, wonderful boys
This is your world. Shape it or someone else will. -Gary Lew