Don't compare just by the listed sizes, they're like t-shirt sizes. One manufacturer's 55 can fit like another's 57.
Stack and reach are a good place to start instead. That's the vertical and horizontal distance between the bottom bracket and top of the headtube. Less stack means the bars will be lower, unless you make up the difference with spacers. Less reach will bring the bars closer to you unless you compensate with a longer stem.
Another thing to be aware of is seat tube angle. A track bike with a 75 degree seat tube is going to put the saddle further back than one with a road-like 73 or 73.5 angle, even if they were built with the same length top tube and same amount of reach. The slacker seat tube will effectively add reach from the saddle to the bars, but also put the pedals further forward. Up to you whether that's a plus or minus. Of course you can move the saddle around to compensate for the reach, but you should really do that to dial in your leg position and not your cockpit.
Now to compare: assuming you're riding a 55cm Cordoba now, that's actually not all that far off the 53cm Steamroller for example.
Cordoba: 524mm stack, 410mm reach.
Steamroller 53cm: 531mm stack, 394mm reach.
Steamroller 56cm: 559mm stack, 402mm reach
And just comparing the Steamroller and Big Block, they are really close in the 56 and 55 sizes. If you fit well on the Big Block you could consider the Steamroller too. So I'd look at your current setup, figure out if you think you need to size up, and start comparing geometry charts.