I just picked up a Smart Keyboard Folio for a discount from bestbuy. I already have the MK. I think the MK will be my "around the house" keyboard left at my desk. The SKF will be the one I use to transport my iPad when mobile.
For me the SKF lets the iPad still be the iPad. I used it folded over a lot, the weight is a substantially lower when you are carrying an iPad and a laptop in your bag. And if I am using my iPad out, it is usually either by itself (Where I am using it as a tablet) or next to my Macbook Air - so I don't need a trackpad.
The MK is substantially better in so many ways - trackpad, super stable, same footprint, screen is elevated, better angles. But it fails in one regard - it is bulky, heavy and a pain to get your iPad out of if you just want to use it as a tablet.
So I think the formula is this - if you want a standalone iOS laptop - MK all the way. If you want primarily a tablet with the ability to type things - SKF.