I don't know, I prefer MXE over ketamine in some situations... but it's not better, nor does it replace it. When I'm rolling or on LSD, I reach for the ketamine to hole the fuck out into space.
If I'm on 2C-B or something though, or even just looking for some dissociation, I grab the MXE because it lasts 3 times as long and I don't have to go through a half gram just to stay high.
Not to mention, plugged MXE is the fucking bee's knees. Like melting off into a dissociated bubble of distortion that surrounds normal life