AR Build - 6mm Arc or 6.5 Grendel?

[mavracer]

The arc is really enticing to me, if it had been out when I went down the Valkyrie rabbit hole I think I would have gone that way.

 

[CapnMac]

For my 2¢, if you are looking at a light, handy, 16" barrel set up, the ARC is probably the choice.
Now, if you were going for 'heavier,' say, 18-20" barrel, solid tube handguard, bipod, etc., then Grendel.

Mind, I have some lust for a buddy's 22" heavy barrel, fixed stock Grendel as it's one sweet varmint terror.
And I have this itch to build an XM177 clone in 6 ARC just for the fun factor.