With LEDE 17.01.0 for me the DIR-860l crashes when used with SQM. But there have been reports that this has been fixed, see: DIR-860L B1 Firmware Question
I will be able to test this tonight or tomorrow. Unless this issue has been fixed, I would recommend the Archer C7 as the router, so that bufferbloat can be kept under control. If it has been fixed, then it doesn't really matter which one you will pick as both routers will be able to handle those speeds with cake. The DIR-860l will have a lot more CPU headroom though, so if you plan on getting a speed upgrade in the future, or if you want to run other CPU intensive things on the router (samba, VPN, mediaserver, etc) as well, then the Dir-860l will be the better pick.