Whether or not you will get to your resort quicker by DME or car service is pretty much a coin flip. If there are any substantial delays at baggage claim, then DME will likely be faster. If not, the car service might beat it by 5 or 10 minutes or so.
I've been lucky -- my two DME times, froim airplane exit to resort drop-off, were 63 minutes and 56 minutes. I don't think a car service would get you to your resort much quicker than that, if you have to stop at baggage claim first.
Were you talking about having the car service wait for you while you check-in at your resort and then drive you to a park? Because you'd probably get a a park quicker doing that than taking DME and then waiting for a Disney Transport bus.