I ride the Force and what I like about them is the comfort of the 3D molded strap, the simplicity of the binding, the quality (been riding the same pair for 5 seasons), and I like that they're a mid flex binding with enough edge-to-edge response to be aggressive on the bigger trails along with enough lateral flex that allows you to ride rails with ease.
The SF45 is a little stiffer but has adjustable strap positions that will allow you to customize them to the style of riding you're into. I have the Supertitan and I think flux has the best cap strap out there along with extremely comfortable ankle straps and the best ratchets on the market.
I have no knowledge of the 390 but when I tried it last year I found the straps too soft and it was less responsive than my Force. But I don't know if it was set up to be more flexable or if that's how the binding is intended to feel