You said they will bond be older and fixed does this mean you are getting from a rescue? If so you could ask to lol at already bonded pairs
then they are already bonded
But that means double the vet bills ( or more if one of them gets sick ) and double the food and hay bills
If bunnies are babies they need seperate pens / cages etc until neutered and spayed and then 6weeks after desex you can begin to bond them ( even if same sex it’s important to desex first or you risk a fight that could mean they don’t get over it and won’t bond later )
You also have to keep in mind they may not bond even if you do all that. Some just don’t.
As for what is better – that depends. If bunny will live inside , you have time before work and after work ( when bunnies are awake at dusk and dawn ) and you spend that time with your bunny and bond with him / her then he / she will be more than happy without another bunny
If you don’t have too much time ( all bunnies take time – one or two ) then two is best as they are social and need company
I have two singles ( not bonded and live seperately housed) and I don’t be bonding mine as one of mine does not like other bunnies. It’s double the time , double the money , but I love it. I think anyone looking at two needs to be prepared for this or get two already bonded from a rescue ( this is what I would do if getting two as you skip the bonding , skip the wait till desex , and they already love each other )