140 vs 160 mm disc rear for touring?

[FreaK]

I was looking up the Hope RX4 calipers and they are apparently designed for 160 only, both front and rear.
I've tried a 140-160 hydraulic setup before and it felt entirely sufficient, but I was not loaded up, and i was not descending a mountain pass.
Currently I have a fairly basic bike that I'm experimenting with to see what works for me, and the mechanical 160mm setup is far from sufficient, so it's a little hard to gauge. This particular frame is IS mount, so trying the Hopes is a little less straight forward.

Thoughts? Touring experiences?
The commuting side of the equation is particularly rough on brakes as my commute includes descending a high traffic hill in the dirty seasons, with significant braking.

[bm0p700f]

160mm rear. The weight saving is to small to warrant a140mm rotor. Its not about it feeling sufficient. There will be occasions however rare where the 140mm is not.

[jlok]

Don't worry about 160 at the rear. Just slap it on, try to lock it up a few times in test ride. You will adjust your hand force for rear brake accordingly then.

[Marin]

For touring weight is less relevant, and bigger rotors are better for heavy loads - use 160.

[mattr]

For the weight you add going bigger, i'd be looking at going as big as the frame will take front and rear.