I'd say it depends on 2 things primarily...
1) Price. If you can buy the ST4s for the same thing as the ST3, buy the ST4s for the suspension and engine;
2) Do you ride agressively? If not, then the ST3 has ample power and torque for you. If you like a bike that performs better, then buy the ST4s and gear it down to make the power band more usable. The bike is geared way too high stock, and gearing it down makes a tremendous difference in the performance.
1) Price. If you can buy the ST4s for the same thing as the ST3, buy the ST4s for the suspension and engine;
2) Do you ride agressively? If not, then the ST3 has ample power and torque for you. If you like a bike that performs better, then buy the ST4s and gear it down to make the power band more usable. The bike is geared way too high stock, and gearing it down makes a tremendous difference in the performance.