Forum Moderators: Robert Charlton & goodroi
I will recommend same domain (main ecommerce site) in case awards distributed in contest are similar niche as your ecommerce site.
google will basically stop sending us visitors who want to actually BUY something.
That said either sub-domain it or put on other domain. It does not quite fit the main site. MY OPINION. YMMV
And would having the exact match in the subdomain help it rank any better (and increase click-through rates)?