If you are doing a lot of low crawling and using your elbows a lot, I'm yet to find anything better than the Warmbac warmtex elbow pads, though I have always found the non-adjustable to be better. There is some stretch in the strap, so they are more comfortable than the adjustable type, which have a Velcro strap that doesn't stretch. I also think this stretch helps extend the life of the pad, which in my experience tend to fail on the straps before wearing through. They also can't come undone and fall off. The only issue I could see would be if you had particularly small/large arms, though I expect that you could special order some made to measure if you ask Kermit nicely.
My info may be out of date, but I know Warmbac were recently struggling with delivery of the warmtex material (and perhaps neoprene more generally), so you may struggle to find any in stock at the minute.
For less crawly caving, where the elbow pad's main purpose is to protect your oversuit from wearing through, my preference is to use the cut off legs from worn-out long wetsocks. These can be pulled up over the elbow and provide a good degree of protection to the elbow and forearm, but obviously offer less protection than a proper elbow pad. As they wear out, you can just rotate them around to put a less-holey bit on the elbow, so they give a pretty good life, at least doubling the original life of the wetsock.
cheers
