The title pretty much says it all? Is there a security advantage to owning physical bitcoins such as those offered by Casascius? If so is it significant enough to justify the price difference between electronic and physical bitcoins?
Is there a security advantage
Kinda. On one hand, you don't have to worry about getting a virus and losing your coins.
On the other hand, you need to trust that the person who made those physical bitcoins doesn't still have a way to spend them. (They could have saved a copy of the private key for claiming those coins before writing it below the hologram.)