The difference, apart from quality, is the amount of current the device can supply. Look at the Output line on your current charger. The car charger should be able to supply at least that much current (A or mA - 1,000mA = 1 A). If it supplies less, the battery will take longer to charge. If the phone just nbarely charges when you're running, say, Maps, and the car charger supplies less current, the phone battery will actually discharge (slower than without the charger) when it's plugged in and running Maps. If the car charger supplies more current, that's fine - the phone will only draw what it's designed to draw and no more.
You can sometimes find crap for $25 and you can sometimes find well-built chargers for $5. (I've been using an $8 double-USB 2 Amp charger for almost a year with no problem.) Some of the ones sold in dollar stores aren't worth pennies, some are pretty good. Ask around. If your neighbor got one that works well and doesn't feel like it's going to set the car on fire after half an hour of use, and he paid only $5 for it, get one. If it feels like you can twist it apart with 2 fingers, it's probably not worth the time you spent feeling it.
(This is one of those things you have to depend on word of mouth for. Some of those $1 shipping included Chinese chargers on eBay are pretty good, some aren't worth the envelope they come in. I wish I could remember where I got mine, so I could give you all a recommendation, but I think I need to reflash my mental ROM - there are more holes than memories these days.)
I'd definitely go with the USB jack kind, though. If the cable on the one-piece ones go or get caught in a door, you have to buy a new one. If the cable you're using in the USB type goes, any $1 cable will work if you don't have an extra one lying around from something with a microUSB connector that you threw out but kept the cable.