As mill and drill the portal has best capabilities in PCB and wood. For metal the steppers and guides are strong enough but the frame not. Then it must be stronger from aluminum and/or with strengthening features. For me this is now more then OK.
The first spindle I use was a Dremel and air grinder. Nice for testing but not satisfying al my needs. So I ordered a 600W spindle, controllable with 0-10V.