Have used MX2 > MX3 > MX4 and MX4 is just right easy to spread plus clean off, giving good temps.
Used on both CPU+GPU's with custom loop 560 Rad 4x140mm 900rpm Zaward fans, playing BF4 CPU 4820K:4.6GHz 1.34v never goes
over 50'c + SLI 4GB 670 at stock GPU 1:4I'C / GPU 2:44'C at a room ambient 24'c.
Its 21'c room ambient atm CPU core's idling at about 21.8'c to 23.6'c using HWiNFO64 4.42 for monitoring temps and volts.