In my opinion, A wild 383 will typically take down a mild to medium build big block (427ci). But if they are both built for more or less the same idle quality and drive characteristics, the big block should rain supreme.
I think doing a 383 with a set of iron vortecs and a 230ish* @ .050 cam would be very cost effective and probably shine over a stock headed big block. Patriot shows them on the web page with springs for $695. They are machined to acept non vortec intakes as well as vortec intakes.
Now if you can spend the money on heads for the big block, typically cubic inches>weight, it's just harder getting a heavier front end with more power to hook
I'm starting to sound like a Patriot employee, but I jumped on their webpage and they have big block heads as well. The least expensive ones are $1395 set up with .600 lift springs.