Well it should be lighter by a little bit as the engine could be narrower. Also, there will be fewer moving parts, therefore less expensive to build. I haven't ridden a yamaha triple for close to 40 years so I can't say with certainty for modern era engines, but I think the triple is inherently smoother than an inline four. That primary balance thing..I think the torque will develop a little lower in the RPM scale as well.