These planes are very similar...

I've had both, powered by the mighty 110 engine. In my opinion the UCD is a better choice. It's almost a pound lighter than the Harrier and flys a lot lighter on the sticks. Neither plane KE very good but can be done with a lot of stick correction. The Harrier is tougher but the UCD isn't bad except the landing gear block is a bit weak. The UCD will Harrier better, Waterfall is about the same, KE is better with the UCD, Hover is easier with the UCD (easiest of all planes actually), Blenders/flat spins are sensational with the UCD (it will actually do a rising flat spin), UCD is easier to build but not quite as tough.

I liked both planes but I gave the Harrier away in favor of the UCD. I've had 3 UCD60 and 5 UCD46. They are awesome planes. I can't ever see the day that I won't have a UCD to fly. They are just flat fun.

Thanks
Barry