I think humans currently have a hard time deploying a 20km by 20km object in space.
Coming back to the topic, I'd like to see the reasons why both approaches could be beneficial. I see, for example, that for space-based constructions we don't - mostly - have interference from the surface of anything, while for surface-based constructions we have support and resources. Do we have a full analysis which would allow us to say "surface always sux, in-space forewa" or "only l00mers build in space, real men are firmly grounded"? Or, talking about a finer point, deployment only - do we have full justification?