Originally posted by FantasticMrFox Nikon's often get (marginally) higher scores for image quality
But this has been up to a lot of debate. For example, Canon cameras lately seem to get terrible lab review results, lower than the Nikon beginner tier DSLRs. And Pentax often uses the same Sony sensor that is in the Nikon APSC flagship, so the differences should be rather negligible (comes down to AA filter/lack thereof, bit depth, image processing).
AF? Eh, its not that terrible for Pentax. In many tests it has shown that Pentax' low light AF abilities are great. Its just that Pentax often doesn't have as many AF points in the flagship, and that AF.C is not as confident.
Flash system? Yes, you are right. Pentax needs to invest a little more into the overall flash system. Not just the "lightbulbs", but the PTTL/TTL, metering, shutter speed, connectivity, ease of use.. I think flash system and pro-support (fast service centres, lens rentals, etc.) are where Pentax is the furthest from Nikon. But neither of those things are camera-specific; they involve many other factors, support systems