My Personal Preference and Why
I've had my fair share/goes on different motocross bikes, a following to name a few...
Suzuki DRZ 400, Honda's CR-F, Honda CR 500, Kawasaki KX 85 (when i was a kid), Yamaha YZ 125 and Suzuki RM 250, (list is endless).
As mentioned, I’ve tried 2 stroke and 4 stroke bikes and my preference is 2 strokes. Why? Well there is a number of reasons!
PROS (2 Strokes)
Even though the new 4's are up and coming they will never match the power to weight ratio of a 2 stroke, purely because the engine re-evaluates twice as fast. You never get the same buzz. (From my own experience)
(Cheaper to buy/maintain)
2 strokes are far less expensive to buy due to simplicity. They are also far easier to maintain for the same reason. YES, we know 4 strokes are longer lasting, but seriously... as soon as you take it to the tracks and drop it, was it worth the extra expense if it’s just going to become damaged?
(Easier to control)
The plain fact is that they are lighter which makes them easier to move in the air, mainly for doing tricks.
CONS (2 stroke)
2 strokes are not without their cons. But they are far less compared to 4 strokes.
4 stroke riders are always saying "oh bla bla bla, you waist a fair amount of money on oil". My answer to that is "you waist so much money on a 4 stroke which cant take a beating like a light 2 stroke".
PROS (4 strokes)
(Smoother ride for a newbie at motocross)
4 strokes are good if you're just starting out and just getting the hang of riding. 0 revs to 14'000 or what
ever the max is, is far smoother and slower compared to a beastly 2 stroke which has a huge power band increment depending on the make of 2 stroke (normally near the top end of revs).
I don't know this for a fact and "apparently" it's not been scientifically proven. They say due to the fact that oil is partly burnt in the procedure and re-burnt as the piston can't always fully eject the emissions that it's more harmful. BUT the new 2 strokes are far better with emissions now. Older 2 strokes were bad yes, but who rides them :P ?
CONS (4 stroke)
Generally more expensive to maintain and buy. It's been proven and well known that because so much effort has been put into shrinking the 4stroke engines down, when a problem occurs it normally leads on to creating more problems due to the complicated build. This leads to more expense.
The fact that the pistons need 4 vertical movements to produce 1 full cycle/revolution in the cylinder instead of 2 for the 2 stroke the power of a 2stroke is double that of a four. People say the gap is becoming less and less. Give it 50 years and it might be a bit closer...
Everyone has their own view on the two engines but I say, if the bike is used primarily for road use get a four stroke, if it's off-road get two. Don’t mix and match.
I hope I haven’t bored you but I just like to pass on what I’ve been told/what I know from experience.
Enjoy whatever bike you have. We are all on bikes for the same reasons, just different views to why we have them.