Whatever is recommended for your vehicle.
Go to a reputable battery shop and see what they advise.
If they advise anything other than a wet cell, RUN! (Else find out why they advise that...)
I'd advise a few shops in case some have some brand agenda.
A good shop should have fresh batteries due to a reasonable turnover else be properly maintained (unlike many department stores etc).
"Maintenance Free" flooded cells with the "power eye" seem popular and good. (Not that I'd pay for the power eye - they only measure one of the 6 cells, but can trap alternator undercharging - not that "we" would NOT have a dash voltmeter or alarm...)
I'd probably only choose a non-Maintenance-Free if weight was an issue.
Later, go back to the "good shop(s)" and mention what you've selected for your audio battery to hear what they say.