I've only used the Harmony's IR but I can say that the URC gear I have easily transmits 40+ feet. All my gear is in the basement and I have a MX-880 in my bedroom.
You will always need some kind of base station to convert the RF from the remote to IR and attach flashers to the gear.
I have not owned either of these so I will let others comment.
Here is how I see it. Harmony is a great easy to use remote. It will do macro's and the wizard software will walk you through each step. URC was a big step up in how complex of a system you can have. I have to track power states for three different rooms and 4 shared sources. This would not be possible with a Harmony system and this would make for a very unhappy wife.
The URC products I use are from the complete control lineup. The software is a bit daunting a first but I was able to do it myself with a little direction from a friend. I would be glad to help you once you find a dealer to get the remotes and software.