Quick... which way's better (225/273)

Yeah, but I never mentioned anything about the potential between the 273 or 225. I only stated that I personally would not swap a 273 into a later a body.
Not directly, OP asked about 300 hp /6, 273 or wherever, you said 360 or stay /6, so if the OP says no to 360 that only leaves 300 hp /6 over a 273 in your stated options
Let me ask you this. How many 273s did they put in trucks or vans? How many slant sixes did they put in trucks and vans? Stock for stock, 2 bbl slant six vs 2 bbl 273 in a heavy vehicle and you need off idle grunt…
I don't see a /6 having more torque potential than a 273. Torque is Cid which 273 automatically wins and VE% and efficiency don't see a /6 having a clear advantage of even one especially both of those.
Anything outside of that comparison really isn’t apples to apples because you can modify anything as far as your skills and $$$ can take you.
Op is asking about modified, 300 hp.