at the moment i have a pix 525 with an OS V 7.0(4) and ASDM V 5.0(4) i want to upgrade OS and ASDM but in cisco software download i have V 7.2(2) last release.
My question is can i upgrade with a V 7.2(x) or do i need to continue with a V 7.0(x) and what are the differences ?
7.0.4 is FIPS Certified
Well if you ask my opinion then I would suggest you to run 7.2.2 however no version is entirely bugfree
The other option for you would be to upgrade the firewall to 7.0.6, this code has been
seen as quite a stable code
Refer to the following link for the release notes of 7.0.6 and 7.2.2
You can run either the 7.0 train or the 7.2 train. The 7.0 train is more stable, so if you don't need a new feature introduced in 7.2, then I would stay with 7.0(6).
The bulk of the features added between 7.0 and 7.2 are VPN/WebVPN releated features. You can view the release notes for 7.1.1 and 7.2.1 to see the new features added.
Hope it helps,