When done the engagement of the gears will not really cause more damage. After many years of riding street bikes and dirtbike, I have never had issues with a transmission. Not to say that I will not had trouble but I never had. I think it comes down to preference. I prefer to simply grab the gear, its faster than clutching and doesn't cause grinding, for me it has nothing to do with worry about clutch wear. As with mainy things riding style can affect the life of your machine. If you do not jump a motorcycle, you will not have to rebuild your suspension as frequently, If you slow down sooner coming into a corner, or will not have to replace brake pads, If you dont work on race starts you will not need to replace the chain as frequently, If you keep enginge rpms far below redline you will increase engine cycles. We do not do these things however because we prefer ride hard so I believe everything is a tradeoff between riding for perfomrance and riding for endurance. I do not doubt that if you had a side by side comparison, the clutched tranny would possible last longer, however I doubt it would be much different.