Just reinstalled RC4 - I am currently using PF3 - and compared a flight using both programs. I chose a short IFR hop from Auburne (KAUN) to Oakland International (KOAK), the route is KAUN SAC SUNOL KOAK at 6000 ft with a Cessna 310, with landing on RW 28R on the ILS 28R approach. I chose this route because I flew it several times with Pilotedge professional ATC and there are also many recorded RW flights from pilot Jerry W. on youtube with his Twin Cessna. Therefore, I can easily compare the behavior of both products to real world ATC.
Weather and time setting was equal, as was the AI traffic (UT II, 70% Airliner and 30%GA)
Since KAUN is a non towered airport, in RW you need to either depart VFR and pick up IFR clearance in the air, or you call FSS on the phone when on the ground. RC4 simulates the phone call pretty well, you even hear the phone dialing...after approval of the route I was cleared for departure "if not off by..." - which is quite realistic and matches RW as well as PilotEdge ATC. I got my Squawk code and the Departure frequency (RW frequency, entered manually during flight preparations).
In PF3, you need to contact FSS on the radio, using either a default frequency (122.2 I believe) or the one which is in the PF3 database and can be modified by the user. I received a clearance to 4000ft and the departure frequency which I needed to contact when in the air to receive the Squawk code. The DEP frequencies used by PF3 are generic ones, but I believe they can be changed somewhere in a text file.
On both programs you can dial in UNICOM and report takeoff from runway xx. After take off, I switched to DEP: PF3 gave me a Squawk code, but I did not receive a final "Radar contact...". I also had to stay at 4000ft all the way to final vectors. After some initial heading, I was cleared for "own navigation", but had to stay at 4000, while I filed 6000 (maybe too much traffic..?).
RC4 DEP took me over after take off at 3000 ft and vectored me nearly all the way to the first waypoint SAC VOR at 6000 ft, then I was cleared for "own navigation". This not 100% realistic, since in RW and PE you are on your own after 3 minutes or less.
Nothing special here to tell. some frequency changes on the route..again PF3 uses generic frequencies while RC4 takes the frequencies from the P3D database (which are mostly outdated by the way).
RC4 handed me over to Oakland center which is not happening in RW at 6000 ft, while in PF3 I stayed at DEP/APP all the time which is correct, with 2 hand overs I believe. Radio chatter with AI aircraft was more intense and more immersive with PF3.
Vectors to the ILS approach RW 28R for KOAK:
RC4 started vectoring already before my last waypoint SUNOL, which is realistic and happens both in RW and in PilotEdge. However, I was vectored directly to the airport, and around 10 miles away vectored to downwind for 5 minutes, than a 90° turn and a 45° turn to final approach course. At little bit complicated and does not match real world instructions, but it worked without problems and I landed safely. However, initial vectors led me over Mount Diablo, which is I believe 3500 ft high, and has some antennas (obstacles) to which I came pretty close...no ground prox. warnings on Foreflight though, so I guess it was save. In PE and RW, you usually get vectored left of Mount Diablo.
In PF3, I had to fly the filed route until I reached my last waypoint SUNOL (not realistic, both in PE and RW you receive vectors before reaching SUNOL). Shortly before reaching SUNOL, I received vectors to the ILS approach without any further zig/zag vectoring, which was similar to my experience in PE (PilotEdge).
No big difference here between the 2 programs. I propose to change settings in RC4 and PF3 to allow only one runway for landing, the one which is used in RW. In Oakland, this is in 99% of all cases RW 28R for GA airplanes. In RC4 you can easily select the preferred runway from a dropdown menu before you start your flight, in PF3 you need to change settings before loading a flight plan, and it is a bit more complicated: you need to mark all runways which should not be used with an "X".
So, my final remarks: Bot programs have their pro´s and con´s...I will use both of them from time to time when not flying online on PE, which has by far the biggest immersion factor of course