First, let me post my specs;
- Intel Quad Core i7 Processor at 2.93GHz
- Windows Vista Premium 64-Bit
- 12 Gigabytes of DDR-3 1333MHz RAM
- 1.5 Terabyte (1500 Gigabytes) Hard Drive at 7200RPM and 32MB cache
- Nvidia GTX 260 PCI Express Graphics with 896MB of Video RAM
- Two HP1707 17" widescreen monitors
With that said, the worst frame rates I get anywhere in the world in X-Plane is 38fps at KSEA with aftermarket scenery installed. At the same airport in FSX, my frame rate drops into the teens (options set to max in both sims). In the air, I routinely average well over 100fps, flirting with 200 on occasion, depending on what all I have running. Once you get things cranked up and tweaked, all you have to do is to look at a couple of my screen shots to see the details. As far as the aircraft go, there are some that are pretty spartan as far as their layout and quality go, but some of the add-ons that are coming out are fantastic (xB737 comes to mind). It's like the FS series when it was in its infancy. Right now, add-ons are relatively sparse, but with the disbanding of the MSFS developement team, things are starting to take off for X-Plane. The one area that I really don't care much for on X-Plane is the FMC. There are a few add-ons that simulate a better, more functional FMC, but let's remember, there aren't any default FMCs in FS at all, so even a rudimentary FMC is better. I suspect that it won't be long before a fully functional FMS is implemented.
FS also does not simulate bird strikes, hail damage, uneven runways, and so on. On one of my more recent flights, a flock of birds took off just as I was rotating and the #1 engine on my xB737 ingested one, causing immediate engine failure. Even a bloody broken windscreen was simulated. On another take-off, this time from KSEA, I had built up a bit too much ground speed on my takeoff roll and hopped the plane into the air when I crossed over the apex of the runway at about midpoint. From then on, I extended my takeoff roll and not applied full throttle until just before the apex.
Given time, X-Plane will be a serious contender for flight sim's best sim. It still lacks a bit but seems to be catching up fast.
Some screen shots of a freeware B767Leaving Seattle in the default B777