I love thread drift almost as much as I love these American : Russian plane debates :-)
The Mig 15 could be described as a confusing aeroplane to fly, especially near its limits. It doesn't feel like it wants to do what it's doing, nevertheless it usually does it. Conversely, my (very) limited exposure to the Sabre revealed it feels far more at one with its pilot, though it seems to lack a certain ultimate ability in the corners of its flight envelope. The American is certainly easier to fly, but I prefer the lower seat position and smaller, tighter cockpit of the Mig. Of course, variations in model, weights, combat height and speeds, etc., make them bounce off one another in terms of 'which is best'.
If you HAD to choose, it would likely be a personal thing, mostly depending on how you like to feel when you fly your aeroplane. Though if outflown I'd far prefer to take my chances against multiple hits from 0.5" rounds than one from that big old N-37 cannon...