I’ve rented both and read lots of comments about which one people prefer, and I think it comes down to what you’d rather have - a smoother ride (BOB) or easier to collapse and fold when you’re boarding transportation (Citi).
If it’s helpful, we are park warriors which means lots of stroller pushing, so you’d think my husband would prefer the BOB but he STILL prefers the Citi. I think he’s a little scarred from having to fold and stow the BOB under pressure every time we boarded a bus, skyliner or monorail - but we also have to have a double stroller because we have two kiddos. I’ve heard you don’t have to fold as often if it’s a single.
I don’t think you can go wrong either way!