When I made my batch last fall, I went for the sweet apples at the orchard stall on the market. I think they were Spartans and some russet-types, too. I prefer the happy native English varieties than the big, commercial, mass-produced supermarket varieties (if you read up on Pink Lady, the whole concept of an owned and copyrighted fruit is just plain WRONG!), but this time of year the local orchards aren't quite producing yet so you can't be too choosy.
If you use sweet apples, then you can use less dark brown sugar (or molasses)!
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I found apple butter to be REALLY easy to make - certainly less effort than my apple jelly/preserves!