Just to add my $ .02...
I've been a member of VATSIM since 2001 and was a member of SATCO (VATSIM's predecessor) since the mid-1990's. My time on the network has included both acting at an ATC as well as pilot. In those close to 20 years of online flying with a virtual ATC network, I can tell you that it has been an immense help to my ability to communicate and understand what one may call "the ATC mindset". Basically, what they will expect from me as a pilot and what I can expect from ATC. I was copying down IFR clearances before I could drive a car...
Now, I've never actually flown on PilotEdge but I am well aware of what Keith has done with the network and how it works, and I can tell you that it does have some advantages over VATSIM. Not to discount the VATSIM controllers (of which I was one for many years), but VATSIM's consistency and especially the coverage can be spotty at best. Weekly coverage for some ARTCCs can be less than 10% of the time. Of, if you do find an ATC online, they invariably sign off just as you're able to make radio contact. That leads us to the the best time to show up on VATSIM being during an event - which can draw a lot of traffic as well as a lot of ATCs. Events are typically localized to a single ARTCC and/or its adjacent centers. Events can be a great opportunity to experience the best of VATSIM, or it can be an invitation to see the worst - inexperienced controllers, long wait times, forgotten clearances, traffic jams, etc., I've seen it all. But, despite that, they can be a lot of fun, too!
My recommendation would be to check out both but plan to *learn* while flying on PilotEdge - it's the true training tool of the bunch. Get a subscription to PilotEdge and use it to hone your phraseology and understanding of the radar environment with professionals providing your ATC services in SoCal. But, on the flip side of the coin, since VATSIM is free to sign up and use, get an account there as well. Then, use a program like VATTASTIC or VATSPY to determine if an ATC is online in the area you wish to fly. You can sometimes encounter some really professional controllers in areas of the country not currently served by PilotEdge and have a lot of fun flying long distance XCs or zipping around the northeast corridor in solid simulated IMC. I think the ultimate solution is to use both networks to experience a wide range of areas and procedures. Just keep in mind that with either network, you stand a good chance of getting the quality of service that you paid for.