This was an episode I enjoyed too.
Really they seemed polar opposites if you go by this episode alone. Robinson being the impulsive risk taker that people naturally like and Archer being the by the book guy who works twice as hard. Robinson said Archer didn't have what it takes to be a captain, and to be honest I really didn't even start seeing it myself until season 3 or 4.
The prototype ship was also a great nugget. You could look at that thing and just -see- it's descended from the Phoenix and that an Enterprise ship might be the next step. T'Pol showing that she was getting over Evil Vulcan Syndrome, by suggesting naming that nebula after Robinson was a nice touch too.
As for why Archer became captain? Honestly I always attributed that to old fashioned nepotism, being his father designed the engine.