This is probably not the right thread for asking for a comparison between very specific units. Looks like you already got some good info from your topic here: Router recommendation for Openwrt
In the interest of speaking to general stability of the MT6000, it's very solid. The OEM bootloader is extremely forgiving and easy to work with. With just a handful of nuances (e.g. GL.iNET Flint 2 (GL-MT6000) discussions - #1214 by _FailSafe), wireless is fast and stable.
IMHO, most who are experiencing any more significant issues are likely running bleeding-edge builds.