I have two who are 11.5m apart and I am so glad I did (even tho it was an accident!). They are best friends and they love each other so very much. I would do nothing differently. It is hard for the first few months, but once the new bub is settled in and sleeping ok, all you do is correspond naps so they go down the same time (sometimes this means holding the older of the two out a little) and then you have a rest too. I will also say you have to learn to do the housework when they are awake. Playpens are GREAT for the first 4-5 months as this stops the toddler being able to get to the bub and use the new one as a toy. I found that if I asked the toddler to tell mummy if bubs was crying she would and it just all fitted together. It was wonderful, even if stressful to start with. You learn very quickly that if u are feeding the new bub, have a cup ready for the toddler cause they will want to sit on u too, so just tuck them in the other side and put an arm around them while they drink their drink. This way they feel included in that as well.
Seriously. You adapt to whatever situation you are in and in time it becomes if not easy, at least not so stressful.
Goodluck hon on whatever u decide. I'm sure you will love it either way!