thoughts on mechanical vs vacuum secondaries on a daily driver

[williamattop]

How much difference does it really make? MPG? Is one way better with some carbs and not so much with others? Stick or automatic make a difference?
Again, we are talking about a daily driver. My choice (and thought process) has always been vacuum with an automatic transmission for better MPG but I have no hard data to back this up.
Lets hear what you guys think and why.

 

[Bonnewagon]

I have limited experience with mechanical secondaries, but what I had I didn't like. You needed steep gears and free breathing to get the benefits, which I didn't have on a daily driver. I use Q-jets with vacuum secondaries and I adjust them so they don't open until the primaries are almost maxed out. That gives me good crisp acceleration without bogging.