This is what DannyBai said about the ws99 vs pro 900: "PRO900's are recessed in the mids and sibilant as all get out. Not a good sounding headphones at all. 99's blow those out of the water and so do the 77's."
Literally every thread about the Pro 900s mention the peculiar long burn in pattern and niche appeal. These are not all-rounders, they are EDM kings. Because OP listens to almost purely electro, these would be amazing for him. OP, you should do some research about these. They are not all-rounders like the WS 99, but specifically they EXCEL at what you're looking for.
The ws99 sounds absolutely wonderful with dub/techno stuff, plus they're bass is extremely fast and solid . Nice tight bass that doesn't overshadow anything, and it has 0 sibilance. The ws99 is apparently better than the 900, and perhaps has much tighter and faster bass. I can't recommend anything more!