Yes, I've owned both of these. I gave ARC 500 to someone else since I found it "visually" confusing.
With WIn500, you have a great deal of information shown on the same screen when looking at TSYS. Hence, you can see the TSYS & corresponding TG's in one screen. Win500 is stable & very easy to use after you master the mechanics.
I tested Win500, PSREdit500 and Scan Control (ScanControl Ver. 7.1) fairly thouroughly. The trial period for ARC500 expired before I had fully tested it but I didn't particularly like the price (for the pro version) and I didn't see any particular advantage anyway. For basic programming, any of these programs is sufficient. They differ in user interface and special features, such as logging and recording. I wound up buying Win500 and PSREdit500. I use them both. If I could have only one, I'd choose Win500.
Arc500 had a bug in it that I found that had something to do with the trunking tables (dont remember exactly what, been awhile). It could be fixed by now. Win500 is pretty much the same thing in a different wrapper but if you need support from the author, then you can pretty much forget it.
After trying all the different choices I found that Win 500 was the winner for me. All of them for me worked exactly as advertised so the end choice truly came down to the way the application was set up. IMO Win 500 has the most user friendly layout.