V1 - Better at QT; better with IO, better round bends than ix but not ci
9500ix - Better at red light and fixed speed cameras like redflex, more noticeable alert when cop is hiding with K band in an area with a known K band false (if on slightly different frequency), generally conditions heightened response to alerts given fewer false positives, 9500ci also has better range sensitivity.
Neither is a perfect product, V1 is clearly the most responsive product and if you are good at interpreting lots of alerts coming in and knowing when to slow down and when to ignore it, then V1 is great. If you aren't then you may find the V1 = drive slowly all the time because you have no idea if the alert is real or false.
Of course using the 9500 to do some of the filtering for you has its own risks - well documented in this forum. From my point of view, I really like the GPS filtering capability, and the red light features. I think I am far less likely to get a red light ticket with my 9500ci. The red light ticket was one of the reasons I gave up on the V1. I have never recieved a QT ticket in my life, so that for me is a lesser concern. The GPS filtering also heightens my response to alerts, and because it blocks out only slices and not the entire band, it works quite well (not delusional here - I know there is a risk of false negatives but I haven't had a real alert blocked out yet).
Plus with all these things, you have to be super vigilant. The best detector is your eyes, and knowing my 9500ci has a gap against QT makes me vigilant. With the V1 my problem was that in an urban environment, it was so noisy, my initial reaction to an alert would be to ignore it unless I see something which kind of defeats the point of a radar detector.