Reactor

Pros:
1) You can do sharp pattern or 3d. Its a very good docile pattern flier if you prop right
2) Its very light, low maintainence
3) Two piece wing is much sturdier and easy to carry
4) Sharp precision and 3d is possible

Cons:
1) The LG Block is hopeless. If you land hard it will break. The real reason is that it is no block, just ply on which the LG is mounted. The best fix is to reinforce with CF bars from the top meaning you need to take the canopy off and cut open the covering. GP would have done better with a single piece LG. Or you can buy a single piece LG seperately
2) The wings are thin, so it needs to go forward to fly. If you deadstick in the vertical or otherwise, you wont be able to control unless it has gained some airspeed which you can only get if you lose some height (if you have height)
3) Once you reinforce it, either before or after a crash, it gains weight
4) It can take max 14" prop, that too with larger 2.75" wheels. You need to replace the stock wheels

I dont have a UCD but I have a similar airplane called Topstar from Phoenix. That one is 60 size but I have readup enough on the 50 size as well. I guess thats the one you are looking at

Pros:
1) Easy flying airplane, great to fly to get your confidence back, especially after a break
2) Decently sturdily built but no beetter or worse than the reactor 46
3) Doesnt need forward speed to fly. Even after you completely stall it, it will be controllable

Cons:
1) Not as stable as the Reactor in winds
2) You cant fly it fast. The wing is thick, especially at the leading edge. If you do fly fast, the airflow will seperate behing the max camber and cause flutter
3) Prone to flutter. The large control surfaces and fat wing add to this problem
4) 3d capabilities are more mushy, not as sharp as the Reactor. Think of it as a lot of resistance to do 3d
5) Limited pattern capabilities since it cant handle speed
6) In any wind it will be a handful to land

I cant report on the setup issues in the UCD because I dont have that airplane but I have owned 3 Reactors (one I crashed when the engine cut at 15m high hover, there wasnt enough height to recover), one I fly now is scratch&dent and another scratch&dent is still in the box. The only reason I have had three is because I cant get any of the competing on Tower. I also have a Reactor Bipe though, its supposed to be much better but is still in box. It really depends on how you like to fly. I like to fly nice and slow, hence I lean more towards my Topstar (UCD60) with the 91 onboard. But for sunday flying-sports-pattern-hybrid-3d, its the Reactor

I will throw another in the fray- how about the H9 Showtime 50?

Ameyam