On the 10.5 I swapped between the cover and keyboard regularly. I didn’t like doing that, but that fold over bump and added weight kind of forced it.
On the 11, I bought both as well but have not been swapping out at all. I think I may actually return the Smart Cover portfolio and keep the keyboard.
The keyboard is now more balanced. No more origami folds which takes away some added weight as well. It is solid, previous versions were a little floppy. I could be wrong, but I think the complaints on the typing noise may be coming from those coming from a standard type keyboard used to a longer travel in the keys. That muscle memory may have you clicking the keys harder which will make it noisier. I have one of the newer keyboards on my MacBook Pro, the key travel is the same, so I’m not getting the clicking.
I love that it now offers front and back protection. It always drove me nuts that Apple offered no rear protection at all on the 10.5. The other complaint people have is that you can’t prop it like you can with the smart cover, but keeping it up in keyboard mode works just as good and will never tip over.
My suggestion is buy and try both, and return the one you don’t want.