Bishop Pass 30F/-1C

Big Agnes generally has better quality control in my experience, but honestly both of those bags are solid choices for summer camping. The Bishop Pass might pack down a bit smaller if that matters to you Have you considered the REI Co-op Magma 30? It's in the same price range and gets way better reviews than either of those

Spec-wise they're pretty close: Greystone 30 is a value down bag (600-ish fill, 1 lb 13 oz range) and the Bishop Pass 30 is a tiny bit lighter with slightly higher fill (650 duck down) and a legit EN comfort around 40F. In real life that means the Bishop Pass is usually a safer bet if you care about warmth-to-weight and pack size.

I really enjoy my mountain hardwear bishop pass. It’s not top of the line though. It’s rated 15* Fahrenheit, 2.5 lbs (just over a kilo), and packs to a decent size (not super small but not huge). For reference I usually backpack in the sierra Nevada range of California. So average nightly temps are around freezing. I would recommend this bag but of course you can get nicer if you have a larger budget. I think the two most important things to consider are nightly temps and material: 1) do you really want a -9*C bag? I’m not sure how cold it really gets where you are but I feel like there is a good chance you are going to be dripping in sweat with that for a lot of nights that aren’t mid winter. 2) synthetic vs natural down. I prefer natural because it’s so fluffy and warm. But both have their pros and cons. Side note: not even sure if mountain hardware is offered in NZ lol

If you're not into making your own synthetic quilt as suggested above, some sleeping bags come in both a right hand zipper and a left hand zipper and can be joined together at the zippers. Looking now I'm seeing fewer options that do this than before. ☹️ For example the Women's and Men's Mountain Hardwear Bishop Pass bags are left and right zipper respectively, but neither the Kelty Cosmic Down 20 nor the REI Magma bags seem to come in alternating zipper sides. Mountain Hardwear Lamina Eco AF comes in both left and right zips. It's a synthetic bag so it's cheaper but will be a bit heavier and take up more space in your pack than a down bag. But so would a MYOG quilt as described elsewhere.

Thats good to know! Thanks I only discovered them recently by accident when I was trying to find a midlayer fjallraven in my size and the quality of that from haglöfs blew me away I ended up getting the mountain hardware bishop bag because of the advertised range being better and the goretex that mountain hardware makes it with. Im canadian and will be using it in the outback which means possible water exposure in the canoe and in the winter; which our winters which i assumed is pretty comparable to your winters which is why I appreciate my fjallraven stuff so much. But I think ill be keeping Haglöfs' bags in mind for when anyone i know is shopping replacements or upgrades