You can be sure that there is a better battery than the one any bike comes with. OEM batteries, like all off the shelf parts, are the least expensive the bike builder deems necessary. This is why your bike didn't cost you $50K.
I don't know if they even make them anymore, but the only aftermarket battery I ever had that was worse than any OEM one I ever saw was a yumicron. I had to go on an unexpected 3 week trip about a month after installing it and, when I got back, it was so badly sulfated as to be unusable.
