I consistently use the method ...
... of tying the tippet to the trailing fly off the bend of the hook of the lead fly.
With very small fish, there is some tendency for them to bump the lead fly away, because of the tippet on both ends of the fly, to my way of thinking, without hooking up. Not that most of those little guys do that, just a noticeable number of them.
With larger fish, I don't see any trend in that regard. And I've never noticed the difference in takes on the nymphs and dries that Mike mentioned. Not saying that it isn't happening - just something that I haven't been aware of, or that I've dealt with without being really conscious of it ??
John