I had a Valentine One last year and nothing could beat it. My mates dad had one of the Bell ones where the radar is in the grill, and the range was poor in comparison. The Euro 550 are also very good. The Valentine also has arrows that point in the direction of the radar which also worked very well....
I did a lot of research before I bought one, and Id have to agree to go for the GPRS one though, although to have maximum protection you would need both as they dont pick up policemen discuised as bushes with a hairdryer....
Hope this helps mate