Compare Apples to Apples
250cc to 250cc two stroke wins hands down, for now. This is the way it is, but most likely will not always be. Can a four stroke be simple, cheap, dependable and light? Yes. Just look at your lawn mower, about as simple as it gets. School kids have rebuilt them in shop class for years.
Can you get torque out of a two stroke? Yes. Look at a Detroit deisel, they have been an option to over the road truckers since the first diesel appeared. A dragster can produce insane amounts of horsepower at extreme RPM's. A two stroke that is fuel and oil injected can be deemed complicated, untuneable and heavy, but they are smooth running, low emissions, and easy starting.
The way it is now, concerning dirt bikes, there is no real way to compare them. It's like comparing a corvette to a mack truck. Could each be modified to perform the others task, to a certain extent they could. Would they perform as well as the other, absolutely not, but in some cases performance may be acceptable. Just like a 450cc four stroke in a 250cc two stroke motorcross race. Or the old yz250wr with the heavier flywheel and wide ratio transmission produced to compete with enduros.
The real question is what are you using it for and what do you expect to get out of it. That's it, plain and simple. If you want to motocross a four stroke you'll need a couple hundred more cc's. If you want to baja a two stroke you'll need more weight on your engines moving parts, kinetic energy.
Don't kid yourself two strokers, four strokes will become lighter, stronger and more simple, and will eventually take the two strokes place. It all has to do with the government, tree huggers, and emission controls. But you can take comfort in the fact that eventually even the fours will suffer the same fate, maybe to electricity.
The next great debate...ELECTRIC VS GAS... Sound familiar?