Dave- Are you considering a new build? Or are these boats you are considering used boats already on the market? If used, I would probably go with the one that is set up the best for your use and in the best condition. If new, the Lowell is going to cost less than the Wesmac, but the Wesmac resale will be better. So spend less now and get less later, or spend more now and get more later.
The Lowell is 3' shorter in length, but about 6" wider. I think the Lowell is going to offer a softer head sea ride, it is deep up front and built down. I don't think there is a DE boat made that will offer a softer ride than the Lowell boats. The 46' Wesmac and the 43' Lowell are my dream boats if I ever had the money to build one.