You still haven't said from where to Universal. If from the airport, a cab will definitely be cheaper than Mears. I think even Tiffany Town Car might be cheaper than Mears with 4 people.
A general rule of thumb with van services that charge per person vs. cabs is that once you have at least 3 people, a cab is the better option. It can even be a better option when there are only 2 people sometimes. Of course, there can be exceptions to this is some places, but it has always been the case when I've inquired.