In reply to andyd1970:
I think another thing to consider is what you are going to be doing when you need said waterproof, and also whether you are carrying any emergency bivi gear.
If you are going to carry on with whatever you had planned, then you need a good breathable hard wearing waterproof that would complement your emergency gear.
If you are going to retreat, then a simple waterproofish jacket should suffice.
For 10 consecutive seasons in the Alps, in the 80s/90s, the only waterproof I carried was a £10 Regatta cagoule. Used it a couple of times when retreating in snow or rain, and occasionally as an extra layer when sitting around.