I have a beltronics and it *****. It rated real high with testing, but I've had V1 before and it is definitely the best.
Depends on which beltronics model, I think. The STi-R Plus is the same model as the ****** 9500ci with some slight firmware differences.
The best detector is the V1, but the ****** 9500ci/STi-R comes really close and has a slew of modern features.
The V1 is the most chatty by far (false positives as well), but has patented directional indicators and number of signals (using dual antennae).
The ****** has less falsing at the risk of suppressing a real positive, but also has an updatable list of non-radar risks, like known red light camera and speed cam positions. Also has the ability (ad $$) to hook into subscription based ****** Live! where crowd sourcing and app based 'navigation' can show new entries in real time.
The 9500ci/STi-R (specifically over the 9500ix and Magnum etc.) can also be integrated with the laser shifter ZR4 (read jammer), a decent laser jammer according to everything I've read. The 9500ci/STi-R is an installed system, whilst the V1 and 9500ix etc are your traditional mount-on-the-windshield affairs.
Also one thing that may be significant is that the Bel/****** are Spectre invisible (radar detector sniffing guns), whilst the Valentine one is definitely not Spectre invisible.
Hope that muddies your waters more.