This topic came to light when I first finally unlocked the KroSol on my new PS3 account. Soon after the store gave me the two Arc Nade brothers in one purchase. And since then I've been favouring the QME over the KroSol for my Gold pug matches on PS3 with my 3 nades limit thanks to Warfighter level 1 (thought next respec card I'm going for more Nades on KroSol).
These two kits are also very comparable because they both have a Nade detonator. One main difference is Arc Nades being both a detonator and primer, while Fire Nades only prime. So while KroSol can only set off fire explosions, MQE can also tech burst too. Both these nades also prime for a very long time for multiple detonations off one nade toss.
Crowd control is obviously favoured by Arc Nades & Tech-Bursts too. So it's not all about dps either, but also what makes the game easier in what makes something OP or not.