In a nutshell, 4 strokes turn lower rpms but with more torque, meaning that you spin a higher pitch prop to make up the difference. The biggest flying difference you'll see is that if you're at 1/4 throttle and gun it, the 4 stroke engine will accelerate the plane immediately whereas the 2 stroke will be a touch slower because of the torque difference at the low end. Yes, fuel economy is better and 4 strokes are quieter and sound much more like a real airplane engine. As for care, 4 strokes aren't as obvious when you find the peak RPM, so it really helps to use a tachometer to tune them. It also lets you check your max rpm so you don't under prop it and float the valves. It's smart to check the valve clearance annually but that's not a difficult task. Sometimes you have to move your fuel tank because the carburetor height is different on a 4 stroke, which can cause fuel draw or siphoning problems.

For brand, OS and Saito both have their loyal followers and seem to be comparable in quality. I have a Magnum 4 stroke and so far am impressed with it. Thunder Tiger also has a good reputation with their 2 stroke engines (I have one and love it) so I'd expect their 4 stroke line to be good. As for lower priced 2 strokes, I'd say Thunder Tiger leads the pack for value while Magnum/ASP (same engines) are cheaper and still trustworthy.