Hi Mark,
You'll get a million opinions on what people think is best, but if you want a high quality, lightweight, Goretex rain jacket, there is one brand which is always well reviewed by hikers, mountaineers, etc, and that's Arcteryx. A Canadian brand (and yes I'm Canadian but lived in Australia and New Zealand for the last 25 years). I've owned plenty of hiking, skiing, mountaineering gear, and I've always found Arc'teryx to be extremely high quality, and their Goretex rain jackets (Arcteryx call them "hard shells") are among the best. Yes, you'll pay a small fortune for them, but they'll last for years and will keep you dry in serious weather in serious places. There will always be reviews from people where a jacket has allegedly leaked or something, but Arcteryx continue to rank among the very best rain jackets according to the pros (whose gear can literally mean the difference between life and death). I've got a lightweight Arcteryx Zeta SL which weighs 277 g (SL = super light) and it's been bulletproof in week long torrential rain in the New Zealand Southern Alps. My other, heavier Arcteryx jacket (Beta LT) has kept me safe and warm in the Canadian Rockies in winter. If you want something which may be overkill, but which you can use in extreme conditions long after your Camino is over, I'd highly recommend looking at them.