If you're doing the kind of technical stuff that makes you worry about ground clearance, the Pro isn't going to go anywhere that the TRD Offroad won't. The PRO will really only be an advantage if you're trying to fly down roads at high speed.
I would buy the regular OR, and put some of the money saved from not buying the Pro into a good set of tires, as both models come with mediocre tires for offroad use. Most of the stuff on the PRO ends up being discarded if the vehicle gets modified, anyway.
Also, keep in mind that the minimum ground clearance number is just that, the MINIMUM. It's going to be measured from the lowest point of the vehicle, which more often than not is the rear differential. So you may only have 9.5" or whatever at that one point, but you could have 15" everywhere else.
On the trail, you just need to know whereabouts your rear diff is, and learn to maneuver around obstacles so that they pass under the axle tube on either side, not the diff itself. Unless you're doing gnarly rock crawling, that number isn't super important. Approach and departure angles are more important, IMO, and a 4R has pretty good numbers on both of those.