Help me understand rebuild vs crate?

I am putting together my plan for a rebuild on my 318 in the fall picking out pistons etc.

It will be a mild street engine. So I am doing a bore and hone, squaring the block etc. New Pistons and heads with roller rockers and new cam/lifters/pushrods.

So my question is all in with me doing all the work it is going to cost me about $3500-4000 to do the rebuild. Machining with balancing is $800, new LAX heads with rockers are $1500. KB 167 +.020 Pistons and rings are $400, New cam, lifters, pushrods, timing chain and gaskets is about another $1000. Then small incidentals, head bolts, fluids total $3500-4k.

I can buy a dressed long block 408 from blueprint for $5000.

I really wanted to rebuild myself, but I am not sure having a mild 318 for 4k is better than a mild 408 for 5k.