Visually speaking, not alot different, story wise VERY different. Starting from scratch, Shepard is a xenophobic male who made all the renegade decisions in ME1. Humans dominate the council, the Rachni are dead, and Wrex is dead.
Here be ye ol' spoilers for ME3:
Paragon: With the help of
, Shepard leads the forces of Citadel space against the Reapers.
Renegade: With the help of
, Shepard leads the dominant human forces against the Reapers.
When I say "leads", I mean in the way he has in ME1/ME2. As we've all seen, not everyone listens to him, no matter what he's done.
I have to say, the Renegade story is playing out to be far more fascinating than the Paragon story. Humans has basically gone from developing sub-light travel to
in the span of a century. What are the consequences of this
, and what impact (beyond what we've seen) will it have on the rest of the galaxy?