Based on your first post. with only a $10 difference in price, I would go for the OS 55AX and not the Evolution engine. it is worth the difference in price.
But being a FOX engine guy, I would go with a Fox engine myself. Fox had last year reintroduced their Fox .50 engines and I would choose it over the other two.
If you have the room for it the Fox .60 or .74 is the way to go.