Hydraulic roller vs solid roller springs is the difference.
I for one have been disappointed with the several e-street heads.
I've owned a set of stealths, not a super impressive head but their good for what they are.
I've only seen small block speed masters, the quality is getting better I think.
I don't know anything about the promaxx.
240 cc runners is plenty to feed what you have, a little more compression wouldn't hurt either.
For camshaft, I just wouldn't run anything hydraulic flat tappet.
That's just my opinion from working at the engine machine shop ....