My 150/3 is almost 10 years old. When the quick disconnect socket wore out last year I figured if I was taking it apart I would replace the brushes. Parts were very reasonably priced . I get it open and less than 1/2 of each brush was worn off. This is after almost daily use in my small professional shop. So I see little reason to buy brushless. Size and weight differences might influence a decision but I haven't played with one of the new ones. Never tried a 150-5 but the 150-3 is only slow when using the coarsest grits like 80 and 60 etc.
I know it's a great machine and wish I'd of made that choice up front! Problem, it's a hard sell to the wife to upgrade one expensive machine for another when I've only had the current one for about a year
Anyone with the 3D visualization skills needed to create a CAD model of something like this for a machine to work with, could probably much more quickly just pick up a chisel and release the dragon from it's wooden prison. It'll be a while yet before Skynet delivers us custom carvings this cool.