I always used to use Tiffany towncar before I moved to FL. I just had my SIL use them & it was $75.00 RT for 5 people in the car. They will also make a 1/2 hour grocery store stop for free.
If you're by yourself, Mears is probably the best way to go...it really depends on how many are in your party! Like CPM said, Tiffany is very economical if you have 3 or more people, and the convenience can't be beat!
I don't know what Mears charges to Universal, but to WDW it's about $26 round trip, pp I think...(might not be exact but it's close )
The taxi is pretty much never the best way to go, IMO.