Easily the Boss GT-10. The boss GT-10 is basically a giant block of metal, with a few plastic buttons and switches on it. You couldn't break it no matter how hard you tried. You can't say the same for the Line 6. The Boss has the "amp control" jack on the back which you could use to switch channels on your MKV. Combine this with the 4-cable method and you've got a killer rig. The Line 6 has great amp models and good effects, while the GT-10 has great amp models and AMAZING effects.
I bought a GT-8 just for the amp control feature, and had no idea that the effects would be as good as they are. The preamps, while great, take a bit of time to properly dial in though.
So yeah, the GT-10 for sure.