My perception is that cherry browns require less force than the MS natural 4000. I say this after comparing the two side by side.
There is another advantage to the cherry browns (or mechanical keyboards in general)... they last a LOT longer. I've had my main work Kinesis for 4 years. The key strokes feel the same today as the day I got it. I would burn through an MS natural 4000 at a rate of 1/year; the spacebar & alt/ctrl keys would become too sticky after.
I have the UHK with Cherry MX Brown switches and my old MS Natural (105KB?) which I had purchased second hand.
I feel that my UHK keys require less force than the Natural.
My Natural has a bit more prominent click points (which require more bundled force at a certain point) but an overall "stickier/mushy" feeling (to be fair, I hadn't cleaned it a lot :)).
My UHK keys feel more springy and one might not particularly notice the click point but I still get good tactile and auditory feedback.
It took me about 2 days to get comfortable with the new keys. Overall the UHK feels smoother and less strenuous.
I hope you can make some sense out of the above, otherwise please feel free to ask for clarification :)
Not all mechanical keyboard switches have the same feel. The advantage uses cherry brown, which is quiet and requires relatively low force.