Things to take into consideration:
Cord length: either coiled or max. 2.1 meter or a replaceable one (DT990 is fixed) or roll-up any long cables to size.
Clamping force (can often be lowered)
Pad material (pleather can get sweaty/sticky)
Airco'd room or not.
On-ears are an option when not wearing glasses and clamping force is low. (Koss PortaPro for instance)
On a warm/hot day all headphones become uncomfortable. There is no 'ventilation' going on in over-ear headphones. It's the pad material that makes it less 'sticky'. In the summer I sometimes get out the DT1350 (DT51P) but these are an acquired taste and would not recommend them to anyone.
Another option is the KSC75 but the ear-clip is not for everyone nor is the seal they give.
The latest KSC75 (and KSC7X) have noticeable less low end and do not sound as good as the old ones.
Koss claims they did not change things but doesn't appear to be true.
Then there is the
Sony MDR-F1 for instance... That one will breath.