Roof vent boots and attic venting?

Can anyone tell me the pros/cons about roof vent boots,should I use the reqular plastic boots or make sure to use lead boots. I have had some problems with the old plastic boot seals cracking/splitting.
Also, should I keep my roof power vent or replace it with one of those whirly birds? I have a power gable vent and fair amount of ridge vent but don’t know if the whirly bird will move enough air compared to the power vent.
Let me know?

The lead flashings will last much longer and can be re-used with each re roof.

Keep the power vent. It will likely exhaust more air passively than the turbine vent, and much more when working.

Thanks for the great advice on the roof boots, I will use lead (I am told squirrels love them)instead of plastic/vinyl boots.
Also, I plan to keep my power vent because you confirmed what I believe, that power vents move more air than the whirly bird. I need all the attic ventilation I can get with S. LA heat and stuffed up soffit vents due to vinyl eaves and not enough perforated slats.