You don't say how you are making the butt joints. Dowel? Biscuit? Metal
brackets? If you don't want to make mortise and tenon joints then
cross-halvings are reasonably quick using a circular saw.

I want it to last so the less holing the better. Probably just 6"
screws through the ends.


With respect, it isn't really a joint if you are relying on "bite" from
screws going along the grain, even if it is glued as well. Or do you mean
screws at an angle going back into the outer timber, i.e. going partly
across the grain. The nearest you will see commercially to your type of
joint is the "pine bed frame" construction where the machine screw going
along the grain goes into the side of a metal cylinder going across the
timber.