I do not believe that there is a ranking difference between widgets.com and widgets.net  (I am getting my ass kicked right now be a couple of .net sites - those rats!).

However, I would not want to use a .net site because a lot of my return customers would by habit type egol.com as the URL.

If the current company still has products and services related to the old sites then I would carefully redirect the PAGES of those sites to equivalent pages on the current company website.  This will have the power of uniting the clans.

As an example... now, instead of having five little sites with fifty links each they will have a much bigger site with 250 links.  That will compete much better for everything.

That is what I would do based upon the limited information that you have provided - but there could be business reasons beyond SEO to do something different.

On the other hand, if the current company is NOT into the same products and services as these older sites then the value of a redirect is a lot less.  If these old sites have good rankings in their product/service areas they could be used to market the products/services of others and still generate income or they could sell the sites to others who are currently in those businesses.