Frame size question

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Looking at the moto Immortal series frame set (full carbon). I currently ride a large compact geo frame (57,58,59,60 equivalent). My choices on the moto are; a 56 cm frame or a 59 cm frame. The 56 cm puts me on the "smaller" frame, the 59 puts me in the "larger" frame. My ideal TT c to c is 575mm (my ideal frame size-standard geo- would be 58cm) so my question is: is it better to go to the smaller frame and put a longer stem with a longer/higher steerer tube (to maintain my current saddle to bar drop) OR go to the larger frame with a shorter stem and shorter steerer tube? does it make any difference? both have similar chainstay lengths and the 59 cm has a 1 cm longer wheelbase. (I can not test ride them)
I've decided to go with a frameset since I would have to replace wheels, tires, saddle, stem, handlebar and crankset (I'll be "swapping" most of these from my other bike) I also know I could get a 58 cm from another manufacturer but I really would like the Immortal.
Any thoughts would be greatly appreciated.

Looking at the moto Immortal series frame set (full carbon). I currently ride a large compact geo frame (57,58,59,60 equivalent). My choices on the moto are; a 56 cm frame or a 59 cm frame. The 56 cm puts me on the "smaller" frame, the 59 puts me in the "larger" frame. My ideal TT c to c is 575mm (my ideal frame size-standard geo- would be 58cm) so my question is: is it better to go to the smaller frame and put a longer stem with a longer/higher steerer tube (to maintain my current saddle to bar drop) OR go to the larger frame with a shorter stem and shorter steerer tube? does it make any difference? both have similar chainstay lengths and the 59 cm has a 1 cm longer wheelbase. (I can not test ride them)
I've decided to go with a frameset since I would have to replace wheels, tires, saddle, stem, handlebar and crankset (I'll be "swapping" most of these from my other bike) I also know I could get a 58 cm from another manufacturer but I really would like the Immortal.
Any thoughts would be greatly appreciated.

Look also at seat tube ANGLE, which as an indirect measure of your femur length, will allow your knee to be in a proper place in reference to your BB and crank arms. If they are both the same, and you can get your hbars proper with regards to your saddle(small frame headtube isn't too short), then it's a matter of asthetics..rise type stem, loooonnnggg seat post vs flatter stem, shorter seatpost.