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Unless your car now has a non-vented battery, you definitely want this connected to avoid fumes and corrosion.
All batteries are vented, even AGM and GEL batteries that fall into the VRLA category of batteries.
And they will vent if you voltage regulator goes belly up and allows the battery to be overcharged.
Personally and based on my experience with batteries at home and at work, I prefer the flooded lead acid battery (FLA). None of those other high-tech batteries have lasted as long...not even close.