I would say, of the two options you presented, that $60 round trip would be cheaper than a cab would...and you would tip either one, so that's irrelevant...but you have another option(s) as well...Mears runs shuttles from the Disney resorts to Universal each day in the am, usually at several times each day...and it's very inexpensive, although, THAT would depend on how many will be in your party too (ie, if it's $15 round trip per person and you have 4 people, then by all means, the town car is the way to go!), but coming back might not be as convenient, so you could take a one way there via Mears and arrange for cab or car for the return. I know they used to have certain times for return and they were often before the park even closed, but they may have changed that, and I thought I heard people saying they had arranged for Mears well after park hours and they spent time at Citywalk, so it's worth looking into! Either way, if you want info or to book Mears, you have to do that in advance, the day before, so either way, you could look into it and if you use them, they will tell you what times they will be offering, I'm sure.
Honestly though, while that is another option, the towncar for $60 round trip sounds like a winner...personal service and no wondering. Also, you would go directly to and from as opposed to having to possibly stop at multiple resorts as you would with Mears.
I'd say the cab would be alot more, in the end for the round trip!
Have fun!
Karen / MsDis / MrsMIB999999