Most people do find 1-2 harder than 2-3, but I didn't.
I was still in baby mode foing from 1-2 as my older two are barely 2 years apart, but dc2 was nearly 4 when dc3 was born and this was much harder for me, because dc3 didn't sleep, yet dc1 and 2 needed to be at school and preschool at set times, and fetched, and to go to their activities, deserved to be able to host and go on playdates just as often as before dc3 was born etc.
This meant I couldn't nap when the baby napped, couldn't stick cbeebies on for the older one and have a slobby relaxed start to the day if I'd only had two seperate hours sleep, and also had to often interupt a long breastfeed which promised to get dc3 off to sleep, because I had to take or fetch one or both of his siblings to/ from somewhere.
For me a 3rd baby with two preschool/ infant school siblings is harder than multiple very small, close in age, children (I also used to childmind when the older one then two were small - all mindees and my own were very close in age) because you're juggling completely different needs and schedules on no sleep.
However if you get a sleeper you'll be fine.
I had all the routine etc down pat and thought I knew it all about getting babies sleeping btw, having my older two in a good routine and having been a childminder and never had a problem getting three babies and toddlers down for naps together, but I discovered that some children just don't sleep no matter what... DC3 has some sensory issues as it tirns out (he's nearly ten now and still rarely sleeps through but also rarely disturbs us in the night as he has lots of strategies now to help him resettle himself).
It waas also a very long time until dc2 played with dc3 as dc1 and 2 were so close - they wete never jealous of dc3 and always protective and loving, but they basically saw him more like a pet I suspect!
I did feel I had a "pair" of children and a much youngr only even with a 4 year gap, until dc3 was about 5. At that point dc1 was just starting to "outgrow" dc2 for the first time as she approached the start of puberty while dc2 was very much still a little boy, and since then dc2 and dc3 have been inseperable.
So it works out in the end, and dc3 is an absolutely incredible child - I've rarely met such a loving, cuddly, thoughtful, creative, hilarious 9 year old boy.
But 2-3 was harder, for me, with age gaps similar to yours.