I have not heard of anyone complaining about the SQ of the FTW. Not sure where that info came from. BUT I am sure there is someone out there that doesnt like it. That being said having an amp that is fully capable of delivering enough power is crucial. While you can feed it 800watts and be happy I was not. Even with EQ they sounded great but I needed more power.
I am not saying you have o have a LOT more power, its just what worked for me. I had about 1100watts going to mine and when I finally upgrade to a much bigger I liked the change. Enough so that I didnt want to go back to a smaller amount again. I had about 4000watts going to each of them.
So capable amp and levels adjusted I would say its pretty hard to beat the 21" in any other 21" size. I do believe the Mal 21" was more sensitive down low but thats about it. They are very similar and should have similar sound characteristics.
I've been using an ep4000, but I see Behringer has the iNUKE series now. I'll have to do some research on those; it sounds like they have more power.