Currently ride a colnago V3 at 54s with a 120mm stem. I am looking into a more relaxed geometry as N+1 and specifically into Basso Astra. Here lies the issue. I dont know whether 56 or a 58 in Basso would suit me better. Recently I tested a BMC Roadmachine at 56cm and that was great fit too. Speaking to the shop, before ordering, they are telling me to go with a 58cm BUT this to me looks BIG (on paper). I tried to run the bikes on bike insights but Basso does not show as an overlay so I can only go by numbers and the numbers look BIG. Hoping someone can chime in and provide some insight for my decision.
Colnago 54s vs Basso 58

Stack 578mm 625.4mm +47.4mm
Reach 390mm 384.4mm -5.6mm
Stack to Reach Ratio 1.48:1 1.63:1

https://bikeinsights.com/compare?geo...57a4001d95e561,