Ask HN: SEO vs. Branding with Domains (keyword.net vs. prefix+keyword.com)

Calling all SEO and branding experts (I understand we may get different answers from each)... As an example, say you are creating a product website about something called "Furble Gurble" - but the .com for that keyword is taken. Would you recommend getting "FurbleGurble.net" or resort to stacking words on the front or end, such as "FreeFurbleGurble.com". Please explain your reasoning from either an SEO or branding point of view.