The mk2 is about 25mm longer in reach size by size. As you’re running a 70mm stem on a medium mk1 I’d definitely go with a large and a 35-50mm stem.
I think I must have had my brain turned off when I posted this!
70mm stem on a medium mk1, so 45mm stem on a medium mk2 for the same reach. The large will feel huge compared to your medium mk1.
To add a bit of clarity to proceedings, the mk1 is shorter travel, smaller, different suspension design etc etc. The mk2 has the 2013/2014/2015 version (they’re all basically identical, just changes in colours and addition of things like bottle cage bolts and stealth dropper routing), then the 2016 version is slightly different geometry (lower BB, longer reach, steeper seat angle) but otherwise the same. The 2017 version is a bigger change with only two dropout positions, different dropouts, different tubing, a bit lighter, etc.
I’m 5’10.5″ on a medium 2014 with a 50mm stem and either 740mm or 800mm bars depending on where I’m riding.