Depends on what you call "good". YaPB and PODBot 2.6mm are PODBot clones, thus their use may be easier for you if you are familiar with PODBot 2.5. Besides, they use PODBot-compatible waypoints, which are pretty wide-spread.
JoeBot is an entirely different bot, and I haven't tested it yet. If you haven't, either, then it's a good moment to check it out now. You will have to upgrade to a new bot anyway, so why not test something totally different?
The same goes for RealBot. Besides, AFAIK, RealBots learn from Human players, which is a very interesting feature.
All of these bots have better navigation than PB 2.5, i.e. they don't always take the same way. This makes them less predictable and more interesting to play against.
I'm a waypointer for PB 2.6mm, thus I'm kind of bound to this bot. But you are more or less "free", so why not take advantage of your situation and test all those bots to see which one suits you best? I would do that if I were in your situation...
Some bots can even be mixed - how about that?