Done both. It simply depends upon the frequency response you want. Sealed, it does roll off early, -3dB roll off point around 50Hz. If the car has cabin gain to compensate, super. Otherwise, you're EQing some. Ported, the -3dB point is down at 30Hz, more then enough extension and generally too much in a car. You will most likely EQ the bottom end down some. However, ported may be preferred in a car that has very minimal cabin gain or gain that starts lower. Sometimes it's simply a preference to EQ up or EQ down. Sealed is traditionally easier to use of course. I do like my ported box a lot though. I've used the DIYMA in my house too, so the flatter, more extended response becomes far more appropriate. Sealed is quite anemic in-house from the early roll off.
The sub works great in either configuration. All you need to worry about is get the frequency response you want to have in the end. Just use the box design that'll make that happen.