Are you meaning the Nikon D300 (obsolete) or the D300s?
For what it's worth, my Canon 1Ds3 has 45 AF points - and I typically use just 1 (usually the one in the centre). With regards to sharpness it's primarily determined by (a) good sharpening technique, and (b) lens optics (in that order in my opinion). It's the job of the lens to deliver the image - in focus - on the sensor, and in this regards, I seriously doubt that you'll see any difference between any of the major brands.
You WILL however find a lot of bias from people when it comes to one brand over the other (for some the brand is almost a religious experience) (in fact if you're ever a bit bored, try asking something like this on any photography site: "Hi - I'm new to photography, and I need help deciding if I should buy a Mac or a PC, a Canon or a Nikon, and should I use UV filters for protection"
The truth is that there's a HUGE overlap in capability between many brands at the same price point.
The Canon 7D is your other option too.