The T5P sounds different from the DT1350. T5P highs are much sharper whereas DT1350 have good tonal balance. "Tesla" is more marketing than anything else. No one to this day can figure out what Tesla actually means in terms of design goals or implementation (other than 1 Tesla magnet in the T1 driver, but obviously not in others). Some of Beyer's classic line headphones are actually better than most of their full sized Tesla line headphones, the lower lines of which are pretty craptastic.
I believe it has something to do with magnetic flux density and a suitable label to give to a headphone line derived from the same design goals (company secret?). As audio is as much art as science it's fairly apt. I appreciate the rare occasion when I am amazed by what craptastic can achieve.
The DT1350 and T50p look very similar, I'm wondering what the hidden differences are.