Depends on how big your place is, what you like to do with your time, etc. We have two 3-seaters (one is a pull-out sleeper, one is 2-seats+loungey bit). Husband used to have an L-shaped overstuffed thing and I hated it. It heavily limited how it could be placed in our living room. So having two separate couches is great.
Most evenings, He and I both sit on what has been dubbed "Mama couch" by our 2yo. Either both sitting up reading, or he'll stretch out on the loungey bit and I'll stretch out across the other two seats. The other couch is affectionately known as "Doggy couch". And that's pretty much who you'll find there
Two big 30kg dogs who think they're too good for the floor
Having two couches has been great for us. We've been known to have weekend movie amrathons and crash out on opposite surfaces. Or when kiddo and I were down sick, she and I shared the bigger couch and Dad had the other to himself (dogs begrudgingly accepted the floor). We also recently had several guests over for dinner and everyone had a comfy spot to sit.
Kiddo also has her own mini-couch which is excellent for wind-down times but mostly she prefers to sit on mine or bounce off the walls
Oh, and in my wider family, youngers always had to cough up their seats for elders. So that meant a bunch of kids on the floor and adults in the seats. I like it better with everyone together.