I use both PSREdit and Win500 to program my PSR 500. Both programs are excellant and I lean towards using PSREdit more frequently than Win500 only because I like PSREdit's user interface better. Also user support is excellant with PSREdit. Mike always responds to questions.
The best person to answer that question is yourself. I may like how one brand of software works and that may be the most irritating piece of software you've ever used. I may hate how another brand works and for you that's the best piece of software ever written.
The major three brands of software for the PSR-500 compatible scanners all offer a free 30 day trial (this is for a fully functional version, not a stripped down version where the useful features don't work until you pay) to allow you to try them out and compare which one works the way you do. They all have the same feature set, but with a somewhat different user interface. Download them all and try them all out to see which you like. They're all worth the small price being charged, but one will probably be a better fit for you than the others.
I will suggest what I always suggest. Try them and see what works for you. As previously mentioned, they all have a trial period so you have time to try them. If you like one or more, then buy the license for it/them.