I understend that there are bugs in A920 is it true? what are the bugs?
Is it worth to add 100$ and buy A925 (instead a920) what are the difference between this two?
There are bugs in every phone. The firmware in the A920 can be upgraded to A925 firmware then the only difference is the case and the screen which on the A920 is 4096 colours and on the A925 is 65K colours but some people have had the screens upgraded on the A920.
Is it worth and extra $100? That's entirely up to you. I have a 920 with A925 firmware and I'm very happy with it.