With how quickly these conversations devolve into arguments...

Ugh. Sounds exhausting.

I think the difference between offering unsoliticed advice that is received neutrally or well, versus unsolicited advice that is received poorly, depends mainly on whether or not the original speaker feels they were being listened to and understood.

If a friend listens to you talk about something, clearly understands what you're saying, and offers unsolicited advice, that's usually not cause for excessive frustration, although sure it can get annoying (and I don't know enough to know if your friends feel like you're a good listener or not, regardless of the unsolicited advice).

But it sounds like the core problem is your BF's unsolicited advice is bad advice, and advice he only could have offered by missing parts of what you said.

Also, it's not 100% clear from your post, but it kind of sounds like the advice he offers is a bit patronizing - an obvious, clear solution he offers and expects you to lap up (even if you have reasons it wouldn't work). That kind of patronizing advice implies almost a lack of trust and respect for your decision-making skills, which I imagine fuels resentment on your part and may be part of why he gets defensive.

In short, maybe you do have a bad habit of offering too much unsolicited advice to your friends, but that doesn't make it okay for your BF to do the same to you, and depending on how he does it, it's very understandable that you'd feel condescended to (you didn't say that, but that's how I'd feel in your shoes I think).