The 20 Tac would require less setback since the front end is essentially the same as the .204 Ruger. You'd have to set the barrel back far enough with the 20 Practical to completely recut the shoulder area. If I were getting an entire new barrel, I'd probably lean towards a Practical for the ease of getting brass and the lack of need to fireform, though the fireform is pretty simple on that one IIRC since it is a simple improved case. For a setback on a .204 Ruger chambered barrel it would probably work better as a 20 Tac.