The first thing I noticed with the 390s is that the footbeds are redone and look much better. There's softer padding under the heels and toes and more supportive foam throughout, making it super comfortable and damp over choppy conditions.
Even though they are not the 390 Boss straps, they're still really comfortable and grippy, making them responsive yet ride-able all day. I loved the UnderWrap.2 heelcup too, because you can really feel the quick pull when charging groomers and making big turns.
In my opinion it is worth it to get the 390 Bosses for the upgraded straps, canted footbeds, and easier adjustability, but this is still a super solid binding with a lot of bang for your buck.