Naturally, you will hear arguments on both sides. I'm on the "get an Apple battery" side when it comes to the integrated parts. Too much trash floating around out there, and too little recourse.
We do very few battery replacements since Apple shifted to the 1000-cycle integrated batteries. In terms of a service part, these are the best batteries Apple has done.
The battery you're after isn't "packaged" and so the risk rises with 3rd party stuff. Yes, there are cheap-ass batteries, but I would compare them to the cheap-ass AA, C, D, etc. you find at the Dollar stores. Mostly junk. The trouble comes when sorting through the junk.
I have seen Apple batteries last a few weeks, but mostly I see them last several years. I'd rather take the risk with 1st party for integrated batteries. Your odds are much longer.