I'd rather have the FoS.
420 achieve points will more than likely be granted just through levelling by exploration, quests, possible rares, dynamic events, garrisons, etc, very very easy to get back.
It makes sense to remove MoP CM in WoD to me, glad I got it, would of been nice to get some other sets and the other two mounts, but I have it on my main so its cool.