Essentially, what you've taken the time to write out mirrors my experiences with the two. The HE-5LE is essentially overlooked for some of the excellent prices that they can sell for on this forum. I, too, eventually waited things out for a bit and then came across the HE-500s. I used them both, going back and forth to evaluate the sound with some of my favorite music. What made me initially love the HE-5LE was still there, yet there was something really special that allowed me to get really attached to the HE-500s. I then knew that I could not own both, as I also had the HE-400s. So, I decided to put my HE-5LEs up for sale. The HE-5LEs were nearly new when I purchased them, so they were of the newest flavor. The new ear pads with the better clips were present along with the nice HifiMAN box. In the end, my premium to switch from the HE-5LE to the HE-500 was only about $75.00. That was a very acceptable amount that I could handle.
I'm going to live with my HE-400s and HE-500s for a long time. I also have my Fostex headphones which I can pull apart and tweak at will with regards to applying subtle sound signature changes. With that, I'm quite content with the 'phones that I own as they bring me much joy.