just gonna say, I honestly feel that it's worth springing for the 3500 seidio.
Mines lasted through 5 months, with really good longevity. And is still kicking with the same (as far as i can tell) amount of capacity.
When I'm not going crazy with power use during school the battery will last around 4 days of pretty normal use.
When it comes to like super power use the battery will last 2 days. And I'm talking about 6-10 hours of browsing the internet, a bunch of texts, music, youtube, xda, etc.
So at least to me, I'd rather pay more (in this case definitely a difference in price) and know I'm getting a good product.