2 different domains, 2 websites for the same business worth?

So as the title says. i have this mobile application that i am building and i have 2 domains. one is the brand name directly .com and the other is a very good direct keyword domain with 20k searches per month and if i even could get to top 5 of the page for that keyword it would be really good. Now my question is. would it be good to build websites on both of them with the same layout i have already built but change the text structures completely? or should i just focus on one domain? All help is appreciated because i am so frustrated and dont know what to do. because i for sure want to rank for the keyword that i have the direct domain to.