Replacement battery for the XV6700?

[Jedi]

i bought my xv6700 used. at 2 bars, it takes 15min for it to die while surfing the web.

at full charge, i could only surf for 45min.

since Verizon states the battery is good for 3-4hrs talk time, i assume the battery is bad.

so for a replacement battery, i was thinking the extended battery (and new backplate).

ebay sellers have both OEM or 3rd party batteries.
which to get?