I would go for the secured card. I got one through BofA last summer, with a limit of $500, in exchange for $99 down. It does help my credit score--the credit limit and existing balance are reported, and it's an account in good standing. The only difference is a descriptor attached to it that says "Secured card." I don't think the FICO calculations are affected in the least by that little disclaimer.
Moreover, the bank is in the process of taking the training wheels off and converting it to an unsecured card--with a $1000 limit--while refunding my $99 plus interest. And two months ago I got approved for another card--CapitalOne. Before I got the unsecured card, I got turned down for CapitalOne, too.
You have to keep in mind that the whole FICO improvement process is a big-time patience game. You can't expect immediate results. You're not going to go from a FICO of 550 to getting approved for $2000 unsecured cards overnight. My advice: take the secured card. It's a start.
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in a credit-scoring postnuclear Stone Age...