I think any older straight stitch sewing machine will have a prettier stitch. First, all the gears are machined metal and don't wear like the newer nylon/plastic gears. The new machines have to move so many ways in order to embroidery and have lost the pretty straight stitch.
I have 2 treadles, 1 hand crank, 10 feather weights and several newer zz machine. If I want a pretty stitch, I get a feather weight out and if I want a work out, go to the treadle. The treadle is a good exerciser for the butt. So, if you have to justify another sewing machine, it's now became a exercise machine.