I know they're very different, i'm trying to decide if i want to use this battery to run when the car is off, that is, an isolated battery, or if i might just go ahead and use it for more power. and the autozone battery is the recommended replacement, i will use a Y adapter to attach it to the vent hose along with the stock battery.
Do not do this. Get a fully sealed battery so there is no chance of it spilling or leaking.
no, it should be fine with that hose. just make sure the extra battery cant fall over. itll be the same thing as you are doing now and that is perfectly safe. obviously an AGM battery will do a lot more good but that vent will work just fine.