I've played enough RQ3 back in the 90s to appreciate its weaknesses for me personally, higher level characters became to much of an exercise in number crunching.
Same with HQ, seven years of gazing into the Abyss that is the numerous details of various cults and the ever expanding background made my head spin!!
Not convienced by MRQ's take yet, but its early days yet and to be fair I've not read all the books (even the core of Glorantha 2nd Age, Cults 1&2 and Magic of Glorantha) in enough depth.
So if I was to play Glorantha these days I would play it out of the box with RQ2 and the Gloranthan Classics
Or I'ld be a Heretic and use the following systems for the following games
Unknown Armies: Lunar Empire, the pcs are members of the lunar cults jostling for immortality and power, risking insanity and all the other wonderful personality disorders that UA's Madness Meters encourage.
Savage Worlds: Rumble the Rubble (Pavis) . Fast furious fun as Orlanthi rebels take on the might of the Lunar Empire!
Burning Wheel: Sun Dome County. BW would nicely support the intense character driven pace that parts of the Sun Dome County write up suggest.