The realistic version of the cockpit is much harder to use, because everything looks smaller (because you're looking through a realistic view; the easy view is zoomed in, sort of like walking around with binoculars on). Also, some of the very nice information on the easy cockpit is gone. This includes, but is not limited to:
Digital Airspeed and Altitude: Now you have to look at those funny-looking scales on your HUD to figure out your airspeed and altitude, though you can change this by pressing V.
AWACS Transmissions: Remember when those messages kept appearing on your HUD, like "MIG-29 TAKING OFF FROM OLENEGORSK", and "SAM RADAR AT BANDAR KOMENYI DETECTED"? An intelligence system like this would be a fighter pilot's dream, but unfortunately it hasn't been invented yet, and the realistic HUD reflects that sad truth.
Weapons: The target boxes are alot smaller, but other than that, not much changes here.
Camera: There is no longer a flashing crosshair on your HUD to tell you when to snap the photo. Use the underbelly camera view to locate your target, and take the picture when the target appears.
Nav System: Your waypoints no longer change automatically. Use PG UP and PG DOWN to select the waypoint.
Velocity Vector: Your flight path marker has now become your nose position indicator and gunsight, and does not move. This makes landings really really HARD. You have to judge your glideslope status by eye, and use the glideslope indicator on the left side of the HUD. If the downward pointing arrow at the top lights up, you're too high, so reduce power and/or lower your flaps. If the upward pointing arrow at the bottom lights up, you are too low, so you should push the throttle up a little bit and climb a few feet. If the green circle lights up, you are on the glideslope (in carrierese, "on the ball") and you are good to go. This means you will have a successfull landing which will not result in your crashing the plane and getting killed.
CLICK FOR A PICTURE OF THE REALISTIC COCKPIT
MiGMan thanks Miles McCorsion