Jim - what's your reasoning for thinking that shareholders would NOT accept the debentures?
If you think it's a scam, then you get nothing likely, but better to get stuck with a debenture than equity. May not help but arguably better, at least in theory.
If it's not a scam, then taking the debenture gives you $9500 on a $500 play after 5 years. If it's not a scam, the stock could go up more (reduction in float argument) or it could be diluted more.
By taking the debenture, you get the fixed return (again, assuming it's not a scam for the sake of argument) and you keep 10% of the shares, which would participate in any low(er) float runup.
Personally, I'd take the debenture.