Ok, I'll offer my 2 cents. I'm not an electronics engineer, so maybe someone will chine in who is, but from my experience you'll see no difference on a stepper driven cnc machine. More important will be a good system match (your driver & motors with the power supply's rating). Excessive continuous load draw on a stepper driven system isn't normal either unless you're using a power supply rated lower than your motor/driver can handle for best performance. That's not to say a linear power supply load will never drop to the levels you mention, but how often you do run all 3 (or 4) axis at or near max at the same time? In my experience linear power supply's are normally pretty heavy duty units with much bigger transformers and huge capacitors. I've used both on cnc machines and can tell no difference other than I've had a regulated power supply go bad, but never a linear supply personally. Switched supplies are normally cheaper. There are some high quality SMPS but it seems the majority used for home build cnc machines and those included with stepper "kits" are mass produced in Asia and use cheaper electronic parts. That's not to say they won't work flawlessly for years. They are normally smaller and lighter if cabinet space is an issue. Some electronic equipment is pretty sensitive to fluctuations & ripples and the regulated power supply will do a better job or may be a necessity, but stepper drivers aren't normally prone to these problems. Just don't use any power supply rated over your drivers 48v limit. If you already have one type or the other, and it's rated for your needs... use it!