I'm not a linguist but...

I'm not a linguist but I like to learn how people pronounce a word.

This may not be accurate. Better is pronounced differently among English native speaker.

UK (non-RP) would likely to omit the T in better.
It sounds like be'er. (imagine Jamie Oliver)

American substitute T with D.
It sounds like bedder.

Australians are more laid-back.
Their better sounds like Beta, like the Greek letter.

New Zealander and South African
Bitter?

Canadians are like American/British hybrid. The follow the American pronunciation (most of the time) while retaining British spelling.

Rest of the world
Pronounce batter and better the same way.

Please comment. My opinion might be different from yours.