This season I bought 4 of the Odyssey pc625 batteries. ( one for each ski)
http://www.odysseybatteries.com/battery/pc625.htm
some folks swear by them, some folks swear at them.
I will let you know if I have any problems, but so far, they are stronger, and longer lasting than the regular $40 batteris I had been buying every year or 2 from wal mart.
the pc 625 costs about $70 each, online, or locally. look for a battery shop that serves a golf course community, they sell alot of batteries.
other folks , whos opinions I trust, will reccommend, the jetworks battery:
http://www.jetworks.net/kb35xc.htm
and some others will swear by the yuasa
I think it boils down to where you are, what you can get, how you take care of your stuff, and how much you want to spend.
Some folks might get by fine with a $40 wal mart battery!