What are the pros/cons for each?
Obviously it's faster in the development process to just throw in email address link like "mailto:contact@brand.com" and not create a contact form. But is it worth the extra few hours of work to build an actual page and place a contact form there?
Maybe the simple answer is actually to do it first as simple email link until you get traction, and then find time to change it.
But - is there a scenario where its better to start with a contact form?
Are security/spam concerns (for that plain email address) apply to the first months of a newly born product, so that you would rather place a contact form already with recaptcha and such?
Just the email should be fine (just make sure it's readable without having to click on the mailto link). If you worry about spam you could use something like support@brand.com in the beginning and switch to another email adress if that get's a problem. In my view, putting an email address on your site builds more trust than a contact form.
I have both a mailto link and contact form on my contact page. I say give the user the choice to use what he or she wants.
The spam I get is surprisingly enough through the form (which doesn't have a captcha).