mainline slope waterfall or slow

[The Sweet Spot]

Ok here is my question. I have a long ridge, much higher than my shack. I am going to tap the trees along the ridge and run them down directly in to my collection tank. Would I be better off to run the mainline at a long direct slope to the collection tank? Or should I run the mainline graduale untill just above the tank and stright down? I have many runs that will be in the same situation. Some will be more than a 30' drop and down to about 15'. Would the amount of trees have anything to do with better vaccume? Any help on this would be great.
Thanks Troy @ The Sweet Spot