1. 4 stroke runs on straight gas, 2 stroke runs on a mix.
2. 2 strokes would be overall stronger then 4 strokes because in a race theres two classes (125 2stroke - 250 fourstroke) and (250 2 stroke - 450 4 stroke) the four strokes have to double there engine size to compete with 2 strokes.

3. 4 strokes have more useable torque, 2 stroke has a strong kicking powerband.

4. 2strokes all around are cheaper then 4 strokes.

5. 4 strokes are usually bigger.

I've ridden both 2 stroke and four stroke and i'd have to say i like 4 stroke better.

2 stroke
Good :
-alot of power
- smaller and lighter
- cheaper

Bad:
- spark plug fouling
- pre mixing gas
- not as efficient
- not as durable

4 stroke
Good:
-lots of torque
-straight gas
-more powerful
-sounds better then a shrieking 2 stroke

Bad:
-loud
-big
-expensive
-heavy