if you have adb and the SDK installed, rooting and installing a custom rom is really easy.
google makes things super easy with their flagship devices;
boot into the bootloader (usually by holding some keys down, in the Galaxy nexus case: volume - + and power)
the type in command
Code:
fastboot oem unlock
and then push recovery by finding a recovery over at
clockworkmod.com/rommanager ( i cant post links until 5 posts
) for your appropriate phone
put it in the root dir and type
Code:
fastboot flash recovery (recoveryname).img
and bang you have an unlocked bootloader and recovery installed. you can then flash the SU.zip found all over XDA and get root. or just flash a custom rom from recovery.
i would definitely go with the nexus tablet, as it will always be the first tablet to get the newest software, and really software now is the only thing that REALLY separates OS' since hardware is subjective to the manufacturer.
hope this helps.
cheers!
feel free to message me for any more questions.