I have both the MK and the Combo touch for the 11". Both have their pros and cons. And which one is better is a matter of priorities.
Pros of the MK:
- the ability to seamlessly move from pure iPad to an iPad with a great keyboard
- extra charging port
- the screen is closer
- lappability is decent
Cons of the MK:
- it's "aesthetically" fragile, especially if you use it on the go, typically in a backpack which has no laptop sleep, just like any Apple iPad's keyboard
- it's won't protect the ipad sides
- it's very expensive
Pros of the Logitech
- Full protection
- More durable
- Possibility to separate the keyboard
- Function row
Cons of the Logitech
- Very hard and annoying to remove if you want to use the iPad naked, it's meant to be left on, which means that the iPad pro 11" becomes much heavier even without the keyboard (heavier than the 12.9")
- Not great on your lap (unless you are on a couch at home). The keyboard is much closer to your belly so less confortable and in some places where space is tight it's almost unusable on your lap. Particularly if you have your pockes full of keys and coins as the keyboard will lay on you pockets (same problem with Surface devices)
- Screen is not as close
In the end it's a matter of priorities. If you have pets or kids who could drop you iPad or if you use it a lot on the go or put it on the ground etc. the Logitech is much safer.
However if you want to enjoy the "lightness" of the iPad when you don't need a keyboard, mainly use it at home, have a laptop pocket in your backpack or use it often on your lap outside your house, then the MK is probably a better solution.
Personally I am in this last camp. I have harly ever used my Logitech, mainly for testing it (but it's there if I need it and I got it for only $100), although I have used the similar Surface devices a lot, while I use the MK rather regularly (it acts as the iPad stand), because most of the time I want to enjoy my iPad as a light device, otherwise I'll use my 12.9. And most of the time I use it without the keyboard and only use the keyboard if I need to write something, which is not often since I use my computer for that.