Ive done both of these as breadh (Intro eco in semester one last year, Finance in the summer)
Finance 1: There's a
very good post in the subject review thread that hits the nail on the head IMO. The most tedious subject imaginable. A continuous bombardment of plug and play formulas. Nauseating assignments.
Intro Eco: Enjoyed this subject very much, although part of that was due to having a wonderful lecturer (Jeff Borland) who I don't think takes the subject anymore. Much more interesting concepts in this subject; I thought Game Theory part of the course was especially interesting. Tutes were more interesting aswell, wasn't just doing a question sheet every week, they varied it with a few games/activities that helped to reinforce the concepts.
In summary, if you want the highest mark, probably Finance (but they're both easy to score high in)
If you want the more interesting subject, don't think twice about it IMO, clearly Eco.