You will find that 99.9% of everything about buying, using , honing , maintaining etc about a straight razor is 'Personal Preference'!!!
'Personally' I lapped my Norton 4/8 on 3M 220 grit wet and dry on the counter-top. However once I got my DMT (325/Medium grit) I've lapped the 4/8 and my Naniwa 12K before each use.
To tell you the truth, I can't notice any difference between the 220 W&D and the DMT! With the exception that the DMT is much easier to use and control!!! :shrug:
PERSONAL PREFERENCE!!!!!!!!!!!!!!