All N64 VC games run in 640 x 480. You're basically getting the same thing if you buy either the Zelda Collectors Edition, OoT/MQ disc, or the VC OoT, resolution-wise.
That said, unless you REALLY think you'll like OoT, I'd skip the OoT/MQ disc and get the Zelda Collectors Edition. You get OoT, Majora's Mask, and (if you get curious) the two NES Zelda games.
"'Casual games' are something the 'Game Industry' invented to explain away the Wii success instead of actually listening or looking at what Nintendo did. There is no 'casual strategy' from Nintendo. 'Accessible strategy', yes, but ‘casual gamers’ is just the 'Game Industry''s polite way of saying what they feel: 'retarded gamers'."
-Sean Malstrom