Slant Six 170 vs. 225

I would venture to say that if you aren’t racing, and even IF both engines were the same HP, that the 225 would offer more torque where you would really need it- on the street accelerating from a stop.
As said, open up the exhaust. But please don’t run duals. If you are one that believes you need to see 2 tips, split a good free flowing single system.