"Investors are still pretty dubious about their founder's $24.4bn buyout offer for the firm, sources whispered to Reuters, with many feeling that the $13.65 a share they'll get is just not enough."
Well they're free to sell on the open market. Oh, I see.. might be a problem since it is currently trading at 12.88 (and opened at 13.04). On June 18th it did peak at $13.74 and closed at $13.40 (and had almost 10 times the usual volume of trades that day).
Short term investors could well be tempted by Icahns higher offer.
On the long term Michael's offer would probably be better as assuming he can turn the company around it shouldn't be unreasonable to expect share value to be higher than Icahn's offer. Perhaps even quite quickly depending on what Dell has in mind.