I think it's a pretty even matchup, but JDS would definitely be the favourite.
JDS has a heavier base, more power and a great chin, but he fades in later rounds, sometimes big.
Gustafsson has better footwork and angles, but less power and and is lighter. It's hard to say that JDS has a better chin, because Gustafsson has taken bombs and not gotten dropped.
Gustafsson is better with trips and in the clinch, but again, he is not as heavy and probably not as strong as JDS.
I see a hard fought decision win for JDS if he fights from the outside. If he takes it to Gustafsson and can walk him down, he might get the stoppage. That is hard if Gustafsson uses his footwork and fights like he did in the Jones fight though.