I recently had the same question (also considered the Vertex Pilot
III) and for all the research I did, it seems like pretty much a toss-
up. In the end I got an A24, and I've been happy with it. BTW, you
can get the A24 with Li-Ion as well though it costs more. Battery
life hasn't been an issue but I've only used it for checking ATIS on
the ramp and listening to the planes flying over my house - its
primary purpose is just as a backup but I haven't yet tried it in-
flight. I also bought the battery pack that you put standard AAs in
(of which I have plenty in my flight bag) in case I ever need it but
forgot to charge it.

If you can find a shop where you can play with both of them, I'd do it
and see which one you like better. I still have never seen a 710 in
person. I think the A24 is reasonably easy to use - I'd change a few
things if I could but no major complaints. But, in general I don't
think you can go wrong either way; if they were the same price I'd
have flipped a coin but the A24 was a bit cheaper so it won out.

todd.