tedster - 4:38 pm on May 5, 2013 (gmt 0)
Bob, I think that decision is more of a long-term user friendliness decision than a technical SEO decision. Long term, user friendliness IS SEO. If you're sure that "overtime i will get rid of 2nd.site.com" then I'd probably lean toward not ever building it. Otherwise, you may be setting up a future bump in the road.