I would take the ABLR over the ELD-X for elk, no question. I have not put the 142 or 150 ABLR into game, but have had good performance with the 129 ABLR (6.5 Creedmoor) on deer (through the spine) and elk (through rib bones) where it held together great. We did have one 168 ABLR (7 RM) fail to exit on a 250 yd shot a caribou, which was a bit surprising. Didn't dig around for the bullet, though.
A lot of people love the ELD-X. I think they are easier to get to shoot accurately than the ABLR, and they kill really well on rib shots. A few buddies love them on game. Sometimes they penetrate great, but also a lot of stories of them blowing up and and lack of penetration. Cup and core bullets won't be as consistent in performance, so no surprise there. There are some similar stories of ABLR, but seems to be a lot fewer, which would be expected with a bonded bullet. Other than being a high BC bullet, there is nothing special about ELDX. They are just a cup and core bullet that benefits from heavier weights and usually a little lower velocities. That makes them great for most applications, but I wouldn't roll the dice on them with elk with better options out there, in the case you have less than an ideal shot and have to break bone or make a quartering shot. I would go with the 140 AB, unless you plan to do the long range game and expect to be taking 600+ yard shots, then maybe the 142 or 150 ABLR.