I found 2 easier than 1, because my first is so sociable that the one thing she can't stand is being alone - until her brother was big enough to play with she needed constant interaction with me, once he was crawling she got him to pretend to be her dog :) Once he could walk and talk he took over a lot of her play needs. She was never really a full time only as I was a child minder from when she was a baby, but that still left a lot of time when the mindees weren't about. She was never noticeably jealous or negative about wither mindees or sibling.
2 was so easy I had a 3rd - left the age gap too long between 2 and 3 (3.5 years from DC2 to DC3 is totally different to barely 2 between DC1 and DC2) and in some ways the set up is so much harder ... However DC3 is the hardest work toddler even taken all on his own, which could be birth order related (keeping up) but I think is largely just him :o
My older 2 fight a lot now but equally play very intensly together for extended periods and are still really close and rely on each other a lot - they are physically the same size and people often ask me which is older, which I think is a reason for both closeness and fighting TBH. Nobody fights with DC3 and both big kids indulge him and look out for him, but only DS2 really genuinely plays "with" him - the gap from DD to DS2 is too big (5.5 years).
1 child, when you usually have 3, is incredibly easy in a lot of ways - esp if out and about - but at home can be hard work as they expect more continuous interaction and become somewhat demanding and stalker- like :o
I often have a house full of kids and find 5 or 6 kids easier than 3 :o but only if at least 2 or 3 aren't mine - lots of kids is easier if they are mostly just visiting, so the kids play without getting on top of each other and you can send the surplus ones home at dinner time :o