A good FBSM is never matter of fact.
A good FBSM is slow and sensual and has a lot of teasing.
A good FBSM can be a good technical massage, if it includes teasing. Teasing in my book should include some ass play.
A great FBSM has both, plus some "AMP GFE," (admiring the client's size, body, etc. giving a hug and/or a kiss on the way out, helping you dress, offering water).

Hope this helps some.