In my opinion, Bob, search engines don't attach any value to domain names.
Maybe they do... in an Interview with Matt Cuts, it was mentioned that they may have some influence in ranking.
There is a singula reason I advise my clients t opurchase more than a single domain - protection.
By purchasing the most 'similar' alternative DNs, you protect yourself against others attempting to feed of your brand/name/site etc.
SE's such as G seem able to break the words up happily enough - it's down to readability for users that is worth bearing in mind.
If it's short, then it's not much of a problem.
Having a rather large DN though can be cumbersome, and if it isn't physically displayed/viewed as RedWidgetsBoughtAndSold... then it might take a few glances before the read realises what they are looking at.
Whether the SE's give a different value to DNs with/without the hyphen, I don't know.
But having multiples with and without shouldn't make a real difference, as they should technically be 301'd to a single, preferred DN - so any benefit from the DN will most likely only be obtained from 1 DN (due to the others being redirected).
[NOTE: I'm guessing at that - though it would be interesting to find if you can attach a domain for BlueWidgets and redirect to Red Widgets... then see if you rank at all for Blue Widgets