SEO Question regarding website domains?

I'd keep the domains separate and create valuable, keyword optimized content on the vanity domain. Top 10 places to get a great 'insert hamburger or whatever it is that you do' (and of course link to yours as number one). Put it on Wordpress, update it once in a while and start building the natural authority and SEO. Add an opt-in with a freebie giveaway and start building your list for which you an promote your true offer on. Monetize with Adsense or affiliate offers if you can't get them to move to your company's offering. A multi-pronged approach is better in the long-run.