as others have said, it really comes down to your own family dynamics IYKWIM.

For us, what really truly decided was not so much the practicalities or timing but ultimately the heart. There was a clear morning that both DH and I woke up and just knew that it was time (of course that then took 10 months lol).

Our personal experience of 3 years gap has been wondrous! just loving that DD1 is that bit older (toilet trained, sleeping through, communication is clear etc). I guess for me, I have found it easier simply because I dont have two small babies ITMS. But that said, emotionally I just wasnt ready any sooner. and that was really the deciding factor above and beyond the rest.

goodluck with your decision! the time will be right and you will know it when it is