Neither. Buy a 4mm Serval if you're dead set on stopping at 4mm. If not, I'd do a 10 mm Serval. ..but that's more money. Either would be superior to a vitos kit.
Sorry. Misread. You meant you're buying a vitos 4mm crank? If so, I'd do a strong stock cyl 4mm or a 4mm Serval. Not a bigbore stock cyl.