I doubt it - 72 errors is not a lot in my opinion.I guess its relative vs. the overall size of the site in question though and the number of total pages that makes it up. If I had a site of any great size that only had 72 404 errors I would be very happy.
Does the new site have a custom 404 page? sometimes its not even worth 301 redirecting those URLs (i.e., if there isn't a natural fit for the old page on the new site or if there is no real link equity built up against those legacy URLs). A custom 404 will allow you to remove those old legacy URLs from the search index and still provide an improved route into fresh content for the search bots in the meantime.
Ultimately though I think you probably need to look deeper into the ranking drops than the 404 errors.
Best of luck with it.
Ben
I just don't think one variation its necessarily better than the other when it comes to rankings. I really do think it purely boils down to preference of how it looks.