It is a reasonable speculation that McCain would've been worse for the country than Obama.
A McCain administration would've given the Democrats pretty much everything they wanted -- since the Republican Congressional minority couldn't have united in opposition, as they did to Obama.
Plus, we would've had the spectacle of a President who couldn't resist getting involved in every conflict around the globe. And with a Presidential temperament that would brook no dissent.
In the long run, we may have dodged a bullet. Certainly, the 2008 election presented the American public with a choice between the equivalent of Scylla and Charybdis.
However, Rubio seems to be staying clear of that duo any more. He probably still feels like a used ___ after the immigration debacle.