The 2 strokes are lighter by a few pounds and can mount more easy between the crank for a better center of Gravity and cost less and have a life of 1000-6000 miles depending on how you treat them.
The 4 stroke is much smoother, much quieter, and the 4 stroke 48cc Titan will run with and even out run the 70cc 2 strokes. So when you consider the 50cc Titan with the 70cc Dax 2 stroke, the weight is pretty close. Also, when the life of the 2 stroke is nearing its end, the 4 stroke Titan is just getting broken in.Also since the 4 stroke mounts behind you, it allows you to install on a full suspension bike and makes for a super smooth ride, and it is even more quiet to ride with the motor back there, and there is nothing intrusive on the top bar or between your legs. Also.. The Titan 4 stroke is an automatic making for twist and go operation. Also, it makes better torque. Also, the Titan rear mount will allow you to mount to a step through frame making for easy mount and dismounts.
So.. To sum things up, The 2 stroke is the Chevy, The 4 stroke is the Caddie. Some love Chevys, Some love Caddies... Enjoy the ride.....