> Which is easier; interstellar travel or building a dyson sphere?

Assuming that we don't know what we don't know, and we need lots of testing and trial-and-error, a Dyson swarm is more doable because we can iterate a design for a swarm node right here in our solar system, until we get it right.

Sending a ship off to a star and then realizing it has design faults is just unfortunate.