Stability/Popularity is it Phone or OS

So I am a newbie thinking about a BB and I have read some posts on this forum.

I know the 8300 series is the most popular series because it is on every network, most stable, and cheapest.

I also have learned that people have said their battery life and reception(most important thing on a phone right?) has improved with and OS update or a new sim card.

I am not used to smart phones(I call them computers). Usually a phone either sucked or did its job.
Now it seems instead of returning a phone to the store if I had problems I should wait and come on this site and look for an update.

Educate me. 99% sure I am getting an 8900 soon.