Rocksmith would definitelly be harder since you have to produce clean tones for game to recognize. Correct fretting and picking... But you'll have some real guitar skills when you turn off the game.
As a not-so-skilled guitar player, I found Rocksmith to greatly improve my rhythm and to teach me a valuable lesson of "show must go on". When you play alone and make a mistake it's natural to stop and redo that last part. But that's not how you can play with others and not the way you can play Rocksmith. So it teaches you to keep playing whatever happens.
Aparth from these aspects, which are important, I didn't learn much more from Rocksmith. Yes, it does have some musical lessons but my general feeling is that it leads you to follow patterns that scroll down, and not to think about notes/chords/scales involved.
Arguably this depends on how you learn and memorize, but I don't think you can discount the visual element of playing instruments. We do have the dots in the fretboard after all.
What I meant to say is that I looked at the guitar a whole lot when I was starting, but then I spent years playing without looking at the fretboard, often while laying in bed. At first I -had- to look at the fretboard and strings to play properly.
Still, it's not as lush feedback as a video game.