Certainly a two-bed makes more sense financially if you rent out the spare room, but do you really want to do that?
Personally, I couldn't share a two-bed apartment with a tenant on a long-term basis.
I have lived in both and when in the two-bed only ever used the second bedroom for guests from time to time.
Now I live in a 1-bed and any guests stay on the sofa. It's not ideal, but it's fine for a couple of nights.
However I will say, I would like a second bedroom to able to work from and for storage.
However, I think it really comes down to Brendan's earlier question: taking the investment consideration out of it, which would you prefer and are you willing to pay for it?