Need some feedback on an upcoming build.

I've located a NIB, Midwest Super Stinker for a great price.
Browsing the posts here, I take it that this one like a lot of other Midwest designs, has been eliminated from their product line and is somewhat scarce.

What I'd like to know is this:

Would investing in a smaller gasoline engine, say a Brillelli or a Zenoah be a better choice than investing in a Saito, (or similar) 1.8, 4 banger?

Currently, I own a Saito 120 and a 150. Even though the plane is IMAC-legal, I don't fly competition, pattern or anything other than sport. I really am not interested in harrier or 3-D style flying, although a nice vertical would be nice.

Any thoughts?

Thanks,
PM