The full list of workshops is available here:
http://pilotedge.net/workshops. Start at the bottom and work your way up.
Disclaimer: I'm associated with PE, but I'll try to be as objective as possible.
VATSIM and PE provide similar service on paper. In reality, though, they're really nothing like one another.
Put simply, if you're an adult with a job and family, and you want to carve out a block of time (30, 60, 90 minutes, whatever you like) during which you'd like to have predictable, reliable ATC service for your flight, then PE is for you. The ATC is there 15x7 (8am-11pm Pacific). You'll be using the published freqs, there's no controller list.
You will, however, be limited to 40 towered airports and ~150 non-towered airports if you're looking for ATC coverage. For proficiency, that should be plenty, though.
If you want to be able to fly anywhere in the country and don't mind whether ATC is present or not, and you're ok with using an online controller list to look up the frequency (an answer that will change based on who is online at the time, if anyone), then VATSIM is best for you. It's also free.
Additionally, PE has the luxury of setting a higher standard for the controllers than would be required on VATSIM. PE is a network that is 100% designed for pilots. VATSIM is designed to appeal to hobbyist pilots AND hobbyist controllers. They can't set the bar too high, or they lose the interest of a vast number of their controllers.
What this means for you, the real world pilot, is that there is no guarantee that the person who handles your flight on VATSIM will be well-equipped to handle your requests. The majority of traffic on VATSIM is heavy metal going long haul between Bravo/Charlie airports. A spam can practicing approaches is a relatively rare event, and as a result, the handling you receive might be dodgy.
I controlled on VATSIM for around 4000 hours before starting PilotEdge. During those 7 years on VATSIM, I tried to encourage real world pilots to use it as much as possible. After getting zero traction, I realized that the perceived problems with VATSIM were significant enough to warrant building something that was purpose built, from the ground up, to support real world pilot training. That's how PE came about. It's not just a copy of VATSIM with a monthly fee slapped onto it, it's a whole different model.