The difference is that the original 356 type modified to fit 4-lugs look more original in the way they fit, e.g., there is no flat lip around the joining circumference. The lip is a dead give-away to anyone who knows Porsches, but of course so are the Mangel wheels with 8 holes instead of 10.
I'm less interested in my car looking totally original than in it being a better car in every way, which is why I got a set 4-lug cast Mahle and 4-lug forged Fuch wheels to try. Prettiest wheels on the car (to me, a purely subjective thing) wins.
I also don't care that my heater control, parking brake lever, and turn indicators don't look "real" as they work much better than the ones on my old 1956 Speedster ever did.