Pretty much what
Grandad4 said. I had an L5030HSTC and was happy with it, kind of skeptical of all the testimonials on how great the HST+ was. I can't use my left leg well enough to operate left foot braking, so to avoid them, exposed hydraulics and cruise control on the L60, I traded my L5030 for an L5740 HST+ and I'm a convert, love it.
No doubt the MX is a great tractor, but for me the GL was worth the extra money. I imagine if you put an L6060 side by side with an MX5800 on the same job with the same driver skills, both will finish pretty darn close, it will just be easier on the L60. I grew up farming on old crash box tractors and no power steering, now with the passage of time, I'm all about easy.
Basically "is it worth the extra money" is going to be an individual thing.