Hi,I personally think the decision would be very subjective. I am hoping my pointers below will help,1. Creating a new site is a hardwork from SEO perspective, it does help by having the site is a sister site.On the other hand, a 'sister' site with reference to the other successful website shows the business is growing and as we all know, people like to be involve with successful business.From SEO site, tho it is hardwork, it will be paid off, where having more than 1 strong websites is very advantages as they can support each other.2. Pointing a new domain to a existing cart, I'd say a faster to boost the new 'domain' and getting the new products off the ground since they will be in your existing successful website.From SEO perspective, I think you won't gain as much as another new site.From customer perspective, they may see another product in the shop instead of new business.Hope that helps,AdityaWeb Design Melbourne