As someone who knows both the 5 and 6 from the inside:
The 5 is fine.
At least you can turn the 6 off!
When 6 was introduced I felt it was a little premature, knowing the 5s as I do, they could easily go a few more rounds and are perfectly capable.
The 6 however is a 'generational step up' and has a whole new lashing of security overlay (none of which I am privy). The UPS software is causing a lot of functionality glitches and is proving to be somewhat buggy and unoptimized. The 6 has much greater processing power and might one day become a worthy replacement.