Preference in design? Opinions please

Super drunk right now, but I'm going to say portrait. Most recently I was looking at the Star Wars LCG cards, and the landscape cards from that are reserved for objectives with art that is more panoramic in nature. That seems about right, that landscape orientation would be for the exception to the norm. The exception aspect is relevant here, but there isn't really a feature of the card that justifies the format otherwise (like the aforementioned panoramic artwork). It falls into place better as a portrait.

I'm not sure if "How drunk can I get without my wife noticing" qualifies for a cheers . . . unless we're being British.

I think it really depends. It seems the card is used for reference, so maybe you want to orient the card differently in order for players to notice it's not a part of the game, but rather a reference card.

Most card games are played portrait style (not sure about yours), but the choice is ultimately up to you. Typically, if it needs to stay out on the field and your play cards are played portrait, then make it landscape to indicate it's not a part of the play cards. It's a very easy way for players to distinguish. Character cards, reference cards, static cards would fit in this category, but again that's me.

Short answer: If it's a reference card, I say landscape.