I think PCM2 has summed it up nicely.
I recently chose and shelled out for the P2450H. I can recommend it highly. Having said that, I haven`t seen the B2430H. I`m guessing there`s not a lot of difference in picture quality. The 2430 is slightly cheaper, so if you like the look of it, I`d say that PCM2`s recommendation should be trusted. If you like the squarer look, I can honestly say that I`m very pleased with my monitor.
BTW I did ponder long and hard over which monitor to buy, but eventually narrowed it down to a Samsung, then the P2450H. Not an easy choice of PC Tech, but what is ?