I've come to really like the MFM more than the FMF, because I love Mrs. WS being the center of attention. She deserves all the attention she gets.

Seeing her in such bliss is a huge turn-on for me.
I have read that 40% of respondents to sex surveys list a threesome as their number one fantasy. From what I've also read, and experienced, I would have to say that for men it is a FMF fantasy. Being treated like a king, and as one married vanilla friend of ours put it: "I don't want another man mowing my grass." I think jealousy is the biggest reason these men want a FMF but not a MFM... at least not with their SO, but they'll have no problem being in a MFM with someone else's SO.
Mr. WS