What’s the best sleeping bag without falling for marketing tricks?

Been digging into sleeping bags lately and the opinions are all over the place. Some people swear by certain brands, others say they’re overpriced hype. It’s kind of hard to tell what actually matters vs what just sounds good on paper.

For context, a sleeping bag is basically an insulated cover you use for sleeping outdoors—camping, hiking, backpacking, etc. It’s meant to keep you warm and comfortable in different temperatures, and people usually start researching them when they want better sleep outside or are planning trips in colder conditions.

I’ve been researching this pretty deeply to put together a guide that’s actually useful, not just repeating whatever brands dominate Google. I’ve gone through reviews, specs, and a bunch of articles, but I feel like real experiences matter way more here—especially for something like warmth, durability, and comfort over time. Just trying to make the recommendations more accurate and not steer people toward something that sounds good but disappoints.

A few things I’d love input on:

• What sleeping bag have you used long-term, and how has it actually held up?
• Have you ever bought one that looked great spec-wise but underperformed in real conditions?
• Are the expensive “ultralight” or “premium” options actually worth it, or mostly hype?
• What’s something you didn’t realize mattered until after using one (shape, fill type, zipper quality, etc.)?
• Any brands or models you’d specifically avoid after your experience?
• Who do you think certain types are actually best for vs marketed for?

From what I’ve gathered so far, there are a few main categories—down vs synthetic insulation, and shapes like mummy vs rectangular. Down seems better for warmth-to-weight but more sensitive to moisture, while synthetic is more forgiving but bulkier. Temperature ratings look like a huge source of confusion since they’re often “survival” ratings, not comfort. A lot of marketing seems focused on extreme conditions or ultralight specs that probably don’t matter for most people. Common mistakes seem to be choosing based on lowest temperature rating alone or ignoring fit and real use case. There’s also a pattern where people either overspend on features they don’t need or go too cheap and regret it fast.

Just trying to put together something actually useful and avoid recommending bad options to people.

Would love to hear real experiences before I finalize anything—what’s been worth it and what hasn’t?