Depend on what you want to do with your PSTV...
Assuming if you just wanted to play PS Vita game and emulator, you might want to update it to 3.60 and install whitelist hack and VHBL.
However if you intent to play PSP iso, it best if you can stay at 3.20, as there is no known ePSP kernel exploit on 3.60.
Stay on 3.20, you can load PS1/PSP isos, aside from PSP emulators and the withelist trick works too.
The PS TV can be updated to 3.60 offline using a USB memory anyways, so you can stay in 3.20, download the update now and you will always have the option to upgrade to 3.60 if something from HENkaku insterests you more in the future.