You're moving the goalposts halfway through your own comparison. For Dunlap vs. Cunningham, you're citing scouts who believed that Dunlap projected better to the NFL, while for Michel vs. Chubb you're citing college production. If you look at Cunningham and Dunlap's college stats, you'll see that Dunlap had 19.5 career sacks and 0 INTs, while Cunningham had 18.5 sacks and 1 INT. Dunlap had 26 TFL, while Cunningham had 33. Dunlap had 1 forced fumble, Cunningham had 5. Clearly that's at least partly because Cunningham had a larger body of work, but that body of work is part of the evaluation in its own right, and even if you insisted on averaging it all out you'd still arrive at a purely statistical conclusion that Dunlap was better at sacking the QB while Cunningham's production indicated a more well-rounded skillset. The scouting report wouldn't and didn't say that, but if you're looking purely at the stats with zero context as you're trying to do with Chubb and Michel, that's what they say.
If you were doing the "player A vs. player B" kind of stats comparison that you're attempting with Chubb and Michel, you'd reach a similar conclusion: that stats alone don't clearly show either to be better than the other.
So basically, you've gotta pick a standard and stick with it if you want to make an honest comparison. Michel/Chubb and Cunningham/Dunlap *is* similar for exactly this reason. The stats showed them to be roughly even, while the eye test showed one to project better than the other. In both cases, Belichick took the wrong guy IMO for what I suspect are similar reasons: because he placed a higher premium on perceived versatility that didn't necessarily translate all the way at the pro level in the way he thought it would. I'm not hating on the philosophy, as it's yielded us a lot of good players in its own right, but in these two cases the results pretty much speak for themselves.
The big difference between Cunningham/Dunlap and Michel/Chubb, however, is that I think Michel is actually a good player, so even in picking the 'wrong' guy he still got a running back that I believe in. Unlike with Cunningham, who was just flat-out bad.