Their resumes are about the same. Andre "R Kelly" Dirrell and Bute (past prime) are his best wins. Good wins, but nothing better than Golovkin has done.
GGG has been a lot more impressive. He's dominated all his opponents. DeGale's two best wins were close decisions.
SMW isn't all that talented. DeGale's best wins are against two fighters that have been long out of the ring. After coming back, either didn't have a single world-class win. The best win between both Bute and Dirrell was Derrick Edwards. DeGale hasn't even delved into fighting the other belt-holders in his division, Abraham, Jack, or Chudinov (now Sturm). While Golovkin has already unified with Lemieux. DeGale also struggled with both Dirrell and Bute while Golovkin breezed through his toughest fights.
Obviously when you start to fight at a higher level bouts become more competitive. GGG lost to Dirrell in the AMs and described Bute as the best fighter he's ever fought pro or amateur. So even GGG agrees Dirrells resume is stronger. Breezing thru B-level contenders doesn't make a top p4per.
Amateurs don't count. I guess we could also rank Shiming world class as he beat Ruenroeng in the amateurs. We all saw what happened when they met up in the professional ranks. And Bute also wasn't even ranked in the top 10 at the time. Hell, it's arguable if he still should be ranked in the top 10, and he gave DeGale fits. Murray didn't win a round against Golovkin and took Abraham to the edge.
I would say deGale's wins over Dirrell and Bute trump anything on Golovkin's pro resume but Golovkin looks like he's a bit better P4P so I guess it depends how you choose to rate fighters.
Murray got the German Business vs Abraham otherwise he himself would have a 168 resume equal to DeGale, had he not gotten hometowned vs Martinez he would be clearly above DeGale p4p in his own right. Best win on DeGale resume is Dirrell who is a Bika/Geale/Macklin level guy. Good, not an allstar and he struggled. Hopefully DeGale and GGG will meet to settle the question, because that would be a worthy fight.