Not sure what to say about the Chamonix... we got one for MoS in the sale this summer and it seems like a good little jacket - perhaps a bit more general purpose / high street than things like the Minimus and Ultra range, so the outer fabric's not quite so light, down fill power unknown (I'm guessing 700 European), but overall good quality, and a snip at £59!
I've had a Drishell Minimus jacket for 6 or 7 years now. I do my best to protect it from wet but I have worn it in rain and it's never ended up soaked and useless. It shrugs off snow no problem. It handles light rain and drizzle pretty well, and it's coped with maybe 15 minutes or so of heavy rain a couple of times while I've been tent pitching and unpacking the car. I've clearly not reached its limit, but tbh for any more than that I'd try to protect it under my shell jacket.