There's no question that core-lokts work. Heck, they have been working for many decades before the introduction of the partitions, X-Bullets, etc. However, there is also no doubt that said premium bullets work better. I've shot CLs and they blew apart on hogs. Same thing has happened to my brother. My brother was using my 7mm Rem Mag and shot a 300 pound hog about 50 yards away in the shoulder (bad place). The hog ran off and was never found. At the point of the shot, my brother found blood and chunks of bone. They looked all over for that hog, but never found it. If he would have used an X-bullet, the bullet would have penetrated and killed it. Instead, the CLs wounded him.
I know that a valid argument can be made that if my brother (or anyone else) would have aimed at the pig's head (ear shots are the best), or if he slipped the bullet right behind the grisle plate, then the CLs would have done a better job of putting down that monster. Same thing goes for shooting CLs at elk on lung shots. However, when hunting game, we don't always get the exact shot that we like. Plus, especially with hogs, they are always moving around. As such, it's worth it, in my opininon, that premium bullets such as the Barnes X, etc., are a much better choice.
On medium, thin skinned game like whitetails, there really is no need for an X-Bullet. If anything, an X-bullet is probably the wrong choice because it does not expand as much, or as nice, as a CL or similar plain-jane type bullet.
Zachary