Like most others here, I can't say that my 2 DSs made my life better, per se, but I'm so glad I had them.
I think I'd have felt like I'd missed out if I didn't have them, and I adore them both. Wouldn't be without them.
But - I worry from your OP that it's the right thing for you, or rather, for your DH. There is no doubt that they DO change your life forever, and it does become more unpredictable and chaotic, at least for a while.
However, one thing - your DH wants to go part-time at work, he could potentially be the SAHP with any DC you had, and that would work nicely. There's absolutely no real reason why YOU should be the one to give up your job/career, if he's the one who wishes to do less - he can do the childcare as well.
Re. the rest issue - well, so long as you both took turns to manage the baby at night, and made sure each other got the rest they needed whenever possible, then I think you could manage it - but do YOU think you could manage it? That's what counts. It's not always easy!
I'd also be concerned that your (both of your) mental health might be adversely affected by the changes a baby would inevitably bring. That's not to say that having MH issues should prevent you from having a baby if that's what you want to do - but if you're pretty ambivalent, then I think you need to consider it carefully.
I have a friend who is married to a man who has depression issues, as does she - they've decided between them that children would add too much stress to their lives and their MH, so have decided to never have children. A decision they're happy with, I have to say (and she's too old now).
But not necessarily the right decision for you.
Overall, I would say having children = better than not having them, for me.