I've recently acquired a RX-65, which I purchased off of eBay, and which was manufactured in week 08 of 2007. It has the G7M4 radar horn. For comparison, I also have the V995, manufactured in week 45 of 2006 which has the G1S7 radar horn. It seems that my V995 is slightly less sensitive for K band yet is slightly more sensitive for Ka band. Both radar detectors exhibit a "lag time" where they will display a radar signal which has been turned off or which I have already passed. This is inherent within the Bel designs since it does result in a continuous alert being displayed upon detecting very weak intermittent and distant radar.
The advantage is that you get a steady and continuous alert for very intermittent and weak radar which is being detected. The disadvantage is that a Bel radar detector will continue to display a "fading" radar signal for several seconds after passing a radar source or if an instant-on radar source was suddenly switched off. But, is this disadvantage really a disadvantage? I think not. I would rather have my radar detector displaying a continuous alert for very faint and intermittently detected radar sources which I am approaching since this will much more likely get my attention. Maxon and other RD manufacturers employed the same technique on several of their late 1980s to early 1990s radar detectors.
So I suggest, ignore the fact that Bel RD models have a "lag time" where they will display a fading alert even though the radar threat has either been turned off or when you are well past the actual radar gun, since I think that you will find the weak but continuous alert to intermittent radar signals to be far more desirable.
Interestingly though, I've found that my RX-65 with the G7M4 horn has a much better ramp up compared to my V995 which has the earlier G1S7 radar horn. Note that the firmware packages for both horn models are different, and this would explain the differences in ramp-up. My V995 with the G1S7 radar horn and firmware revision 4.5 has a much slower ramp-up compared to my RX-65 with the G7M4 radar horn and firmware revision 6.3. Yet my V995 seems to have slightly better Ka band sensitivity compared to my RX-65. On the other hand, my RX-65 seems to have slightly better K band sensitivity. Keep in mind that the sensitivity differences are rather slight and seem to be within 2dB of each other.
In a nutshell, it seems that the V995 (with its slower ramp-up) is designed to be a quieter general purpose radar detector which is less annoying for passengers within your car. It also seems that the RX-65 is indeed designed for the professional driver in mind since its ramp-up is much better compared to my V995. Both are very good radar detectors with very similar sensitivities across all radar bands. Yet it seems that the V995 ramp-up is designed for the masses whereas the RX-65's more extreme ramp-up seems to be designed for the truly experienced radar detector owner.
Anyway, that is the way I see it!