In general, how do you decide between Trader and Horse Trader to open?
I just played this set and lost: http://dominion.isotropic.org/gamelog/201202/03/game-20120203-125729-9a2fe120.html but it was a close game. I'm not sure Horse Trader is a better opener, in the absence of attacks. Thoughts?
I think it depends what you mean by faster.
Horse Traders is fast at getting you an early $5, and in a board with Hunting Parties, this makes it an excellent card to go for, especially as later on it becomes an extra buy and extra $ without messing up the reshuffle pattern from a Hunting Party chain. See Turn 7!
Traders is pretty fast at generating Big Money for the mid game, but is slow to start off (as when you first draw it, you're playing a 3 card hand and at best probably getting no more than a silver), so I'd say that it works pretty well with decks where you intend to play one or no actions each turn. Say, Trader / Courtyard, or something like that.
But for this kingdom, I think Horse Traders was a better choice. Loan, otoh, I think was a damn weird choice. The deck thinning effect is counterbalanced by the fact that its another card for Hunting Party to draw, and it can move a load of crap back into the deck from the discard at the end of a Hunting Party chain. The choice of Loan slowed down your opponent, I believe, and was what allowed you to almost keep pace with him.
My own approach would have been Horse Traders / Silver, then Hunting Parties, one Gold, and going for Provinces pretty much only when all the Hunting Parties had gone.