I don't have any problems working with the 125, but I do think the 150 is smoother, it has a better balance, probably due to the bigger surface of the pad. I agree the dust collection with the 150 is very good. On vertical surfaces I mostly use the 150, and I am very used to it so it's never a problem for me. I only use the 125 when the 150 doesn't fit. I was sanding an outside wall the other day, made up of 7 full 8x4 sheets. You really want a 150mm sander for that.