Use or don't use vacuum advance on distributor???????????????????

Don at FBO sets his distribitors up for manifold vac. Had one in my dart. I liked it. Felt I needed less throttle to get it moving compared to the non vac advance dist I had in it before. Also had to turn down the idle with manifold vac. Both caused less gas useage. Still had mechanical set up at like 17 and 35 but with the vac advance hooked up it had close to 50 at idle if I remember correctly.