When we had to change out my Pfaff 130 motor, the local repair person found a compatible motor marketed for my machine, since nobody makes the exact motor that I had. The amperage on the new motor was not nearly as high as on the original, and there was an orientation problem for mounting. Using a hose clamp, my husband was able to mount it securely, and the electrical connections were compatible. My Pfaff does not run as fast now, but it is acceptable. So, yes, there is a difference in power of various sewing machine motors.

I think motor is important but I think other variables are also in play. My machine has a foot with its own internal motor and that helps the machine through tremendous amount of layers. The machine alone by itself is pretty strong and solid but the foot adds even more power to it. I had 2 high end brother made machines, and can tell you my v-series is a huge difference in power than my babylock was and my babylock was a very nice machine, but my brother can sew through anything and sew through it better with cleaner stitching on bulky projects hands down so even within the same brand of high end machines you can see a tremendous difference. I feel my v-series is way more solid and it is also a lot heavier in weight which probably entails higher end parts as someone was stating earlier in a comment on berninas so I believe parts can make a difference as well. There are so many variable in sewing, type and size of needles can even make a huge difference also in sewing thick layers.

I love my kenmore

my grandparents used to recover furniture on their treadle machine for a hobby
grandmother also did all her other sewing on it all her life, like my doll clothes sixty years ago and my wedding quilt