The most significant variation was in the Repeatability test.

Magpul handrails are the most affordable.In the Endurance and Rough Handling tests, both systems passed. The polymer accessories Magpul offered didn’t work well with the KeyMod’s conical nut. Magpul sought a design that worked better with non-metal mount surfaces. Just like the KeyMod, the M-LOK allows for direct accessory attachment. The Modular Loc k, or M-LOK was patented by Magpul Industries and introduced to the market in 2014.

This also allows for picatinny rails to be mounted onto the handguard wherever needed. What's a better handrail?Im looking to replace my handrail on my Stag-15 M4 and want either an MLok or Key Mod handrail in a carbine length.I understand the Keymods have all sorts of mounting accessories but not really familiar with the MLOK system yet.The cheapest KeyMods around $50.Instead of having a hand guard with a picatinny rail attached, the KeyMod was designed so that accessories could be mounted directly onto the rail.

Keymod accessories torque specs