I agree that in the sub $300 range the DT 1350 is the best on ear headphone I own & for short stints, 2 hours or less, it is generally the one I reach for ( over the Senn 25 or v-moda m80). But on- ear headphones make my ears sore so for longer listening sessions, I more often than not reach for the AKG m50s. They still sound really great & are more comfortable for my for longer listening sessions. I think they may be the best value in headphones. All 4 sound even better with a quality portable amp though the DT1350 benefits the most when amped & really separates itself from the others that way.
If you are willing to spend more than $300 or even $500+, then you have lots of other options though I feel you do need really good portable dacs/amps to get the benefits those better headphones can provide. I find the above mentioned gear plenty good enough for portable use. I do my really critical listening at home using my desktop gear.