The shows aren't alike because P&R is about characters who are positive and supportive of each other, its pretty unique in the TV marketplace actually. With Andy off shooting Thor (or whatever movie) this season its actually lost a lot, he was one of the funniest characters for being so dumb yet loveable and always wanting to help, like a big dog. It also has Pawnee as one of the stars, to highlight/exaggerate the highs and lows of small town middle America. B99 is more a generic sitcom set in a police precinct.
B99 was pretty boring for the pilot, but its definitely gotten better each episode and it looks like Fox is really, really behind it with a 22 order episode and placing it after the Superbowl. Hopefully the episode that airs then is really good and gets some ratings momentum. I kinda wish the show would lean more on the comedy side than the "cop" side of things, its more fun to exaggerate really bad cops ala Reno 911 than it is to show a mix of decent and dumb cops, but the Samberg character probably really wouldn't work if they made him too retarded. We also really need to see the personal lives of some of these characters, Terry Crews doing family stuff is gold.