I wore a NF Redpoint Optimus Primaloft jacket the first time I climbed it, and a Patagonia DAS parka the second time. Both times I climbed through the night from C1 (Nido) to the summit in 8-9hrs, not using C2. This was cold, both times, around -25C at 6000m at 3am, and I also wore MH Compressor Primaloft pants both times, which made a significant difference.
Most will climb from C2 though, so won't be climbing as much in the dark and cold, so a mega puffy 8000m type parka is not really necessary, unless you have 8000m plans in the near future, and want to buy just one (!*) jacket. Most 750-800 fill power down jackets with a good hood will do. Also, if you take more time down low (as I do) or pre-acclimatise elsewhere like I did (Cordon del Plata) then you may move faster up high, thus not needing such warm gear. On standard commercial itineraries though, most suffer a slow plod from C2, summiting around noon or later, which means you're mostly in the sun, but of course the wind is often strong.
* In which case you have no place on this forum!