I haven't ridden Chang, but I think that if I would, I would still like Mantis better, because my favorite part of that ride is the whipping around the turns at the end, which Chang doesn't have. One thing I've noticed the last few times I've been to CP, is that the mid-courses on Mantis brake the trains more than they used to..which means the turns aren't nearly as intense as I'm used to them being. Enough complaining though, it's still a good ride.
And I also agree that the trims down the 1st drop are barely noticable. They just slow the trains down enough so the big loop doesn't pull as many g's. as it did before.