I currently ride a size 58 Super Six Evo. My saddle is 790mm high and I run a -8 Deda 120mm stem with Rotundos for ~13 cm drop to the hoods (and yes, I can ride an entire crit in my drops juuuust fine- I'm 6 feet 2 with long arms).
I want to switch from the Rotundos to something without as severe of a downward ramp to the hoods. Doing so means I also lose the 20mm of drop from the bar tops to levers, effectively bringing everything up 20mm.
In order to compensate I'd have to either run a -17 110 or 120mm stem depending on the rear of the bars.
At the same time I can size down to a 56 and get that 20mm and not have to resort to a zany stem, but I also worry about the decrease in wheelbase, decrease in front center, and overall stability. The 56 also reduces reach by about 15mm as a combo of the shorter TT and slacker HTA thus requiring a 130 or 140 stem to get the necessary reach, but with reduced handling.
In real life, would it be that substantial of a difference in handling to either make it a bad idea or make it worth it?
Don't take me too seriously. GramzStrava