Which intake would you use?

You really need a dual plane intake. Manifolds like the performer are designed to be a performance upgrade over the factory 2bbl. Single plane intakes are typically a performance upgrade that really does best with a better cam, heads, exhaust, etc.
With a stock 318, I'm positive you will be happier with a performer.
If all else fails, ignore what we are saying and try both. Nothing but "seat of the pants " feel will really make your decision.