Now that I realize you're considering the units for Deer hunting (my fault, sorry) here are a couple of thoughts:
The units really aren't very different when it comes to trophy potential and they both have plenty of public land with steep, thick canyons.
Unit 30, 3rd season: Green-Chip Unit. Slightly higher success rates than unit 61 over the last few years, but not by much. Some of the bigger bucks migrate into unit 30 so this is somewhat weather dependant. Most of the deer will be in the Northern portions bordering unit 21, and there are plenty of steep, thick canyons. This is an OTC unit for elk so there will be increased hunting pressure from elk hunters in the field.
Unit 61, 2nd season: Green-Chip Unit. There are big bucks here but the deer population has been decling for a few years. Very steep, thick terrain at the top (East side) of the unit. Big bucks can be difficult to locate during 2nd season since they will still be in the high steep stuff (they move lower during later seasons). This is a draw unit for Elk so less overall hunters in the field.