It depends, but I'd say in the beginning you want to get qualitative and not quantitative data. Adds are good for quantitative data, but if you write mails and people respond, they will usually tell you stuff. Most only a bit, but some a lot.
1-to-1 communication is the best way to learn about your potential customers in the beginning. And once you need to learn about them quantitatively, it'll become easier to use adds, because you know the pain points but also the wording of your customers.
1-to-1 communication is the best way to learn about your potential customers in the beginning. And once you need to learn about them quantitatively, it'll become easier to use adds, because you know the pain points but also the wording of your customers.