great question! I was just looking at the TRX-1 myself as an alternative to Uniden.
Currently I have a Uniden BC246T and was thinking about upgrading to either a BCD325P2 and BCD436HP soon. Overall I liked my Uniden as its served its purpose well, mainly monitoring Roseville & Sac County systems with occasional Rocklin, Lincoln, Placer use, except I've always found the speaker to be a little lackluster in volume and clarity. That may give me enough reason to try Whistler.
One thing I have heard is one of the manufacture devices tends to struggle properly decoding P25 systems that broadcast from multiple sites(like Sac). Unfortunately I can't remember which. It would be interesting to see a direct side by side performance comparison.