you should get both... and whichever one you don't use for this build, you can use in your next build.
I was a piezo holdout for a long time. Now I like both. A lot of it is the look you are after. If you want a 1930s look, you may not want a mag pup.
I will tell you that I've had more buzz problems with the mag pups - those were setups that I wired (miswired?) myself.
When I bought pre-wired, no buzz problems.... And a volume control is handy thing.