I own both the TRX1 and a BCD436HP. That in itself tells you something......as Mike has already said, the ideal is actually a hybrid of the two.
IMHO, if you think you will use the receiver just to scan known channels, I'd go for the Whistler. But if you think you'll need to use it to search a lot for new channels, then go for the Uniden. I actually do more of the latter, so favour the Uniden. Ironically, I'm often hunting for NXDN signals, so rely on the Uniden to find them and the Whistler - once programmed up - to scan them. If Uniden add NXDN to the x36HP range, then I'll likely be parking up the TRX1 for a while. As stated earlier, I think it depends a lot on what you will use your scanner for, and what the analogue/digital environment you will use it in looks like.