What's the difference between a 24" and 26" barrel? Um, let me think........2 inches I think. Sorry, I couldn't help it.

2 inches will gain you a little velocity, maybe 50 to possibly 100 fps, though it could be less. The gain in velocity will result in a slightly flatter trajectory and when I say slight I meanvery slight. As far as accuracy is concerned, well, every barrel is a thing unto itself. Either one could be inherently more accurate than the other. There's really no way of telling beforehand. My advice is to buy a rifle brand known for quality and chances are you'll get a good one. I don't know what you're looking to spend, but you should consider looking at a Cooper. They're more expensive than your average Remington, Ruger, etc, but they'll probably beat the pants off of em' in the accuracy department.

Speaking of .243's, I bought a Ruger Compact last year for my son to shoot. One thing I failed to take into account was how much muzzle blast the short 16" barrel produces. It's pretty fierce. Now I wish I had bought something else, something with at least a 22" barrel on it. Oh well, you live and learn.