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Make sure you look at your URL bar when claiming that two URLs are "the same exact landing page". Just because they look the same, that doesn't mean they are the same. A page is defined first and foremost by its location, its URL. If the URL is different, it's not the exact same page

I think that there is a good chance for an increase of total sales by combining the sites.  I vote for this because the two sites have diverse link profiles and combining them will make a big gain in the link diversity and domain authority of the site that remains.  I would merge them with optimism rather than with fear.