To me the Severe and Legion Solid are not close, the Legion is strong with back end pop.
Severe wants to roll the whole lane, I had both balls very close in drillings surfaces were out of box. I changed the Severe to 4000 and used it as a later shift ball which it was very good at.

I never had the FX but the ones I have seen are strong and with backend. I didn't like the MVP, tried it at several surfaces but did not match up. I like the Pearl and GB2 better. Hope this helps some..