I remember that feeling OP, when you have children around that age so you know it's now or never if you don't want a huge gap. I will say (appreciate this is larger families, but it came up on active) that I was really undecided at the time (2 boys also, I won't lie that having a girl was one of the considerations!) but in the end decided that life was just starting to settle, especially as we got out those childcare years and we could start going on lovely holidays, and we had hobbies again, and felt like we started shared interests with our kids rather than just being their guardian if that makes sense? I realised that actually I was really aiming for quality rather than quantity in terms of really wanting to provide for them what I could, that I really relish 1:1 time with my kids, plus time with my husband, plus time for my own hobbies and career, and it's much easier to juggle this with 2 kids. DH got the snip.
Mine are teen/ pre teen now so still relatively early in our parenting journey I suppose, but I have no regrets yet, I am one of those who have felt very relieved going into the teen years that we have the capacity to spend time 1:1, teens needs are very different to young children. I'm not going to say it's harder because I don't play into doom mongering and I don't think it can ever be as time intensive as pre schoolers, but teens require a surprising amount of your bandwidth still that shouldn't be underestimated, and I'm very glad I haven't overcommitted, especially now I spend most of my week working as a taxi! I know this is controversial, and many won't agree, but I think I would struggle to have the depth of relationship I have with my 2 sons if my time and energy had been further divided by another, I will never know, just as those with 3+ will never know how they'd have parented differently with less, but I certainly don't have regrets.