Having had both C60 in a 50s and a XR4 in a size 53 .. it really depends on what you want.
I rode both C60 and XR4 extensively and if you wanted a do it all everyday comfortable ride, the c60 is the bike to go. It really is just all round comfort and a joy to ride. The XR4 however, is a different bike. Its fast, wants to go fast, you can push it to your limits and it'll still as for more. I put it as a bike on a rail gun. Lightning fast , but comfortable at the same time.
I must admit that if i were to take it for a fast spin, the XR4 will be a choice over the c60. If it was a grand fondo event, definitely the c60 over. Either are great bikes, but horses for courses.
This is valuable opinion. Do u have the same wheelset on both bikes? (And tires)
And wondering since im riding C60 in 50s size, and did not buy Bianchi (Specialiissima) in that time (Specialissima in LBS, to buy C60 i had to go to Italy) since 55 was big for me, and 53 like too small (Bianchi suggested 55, and had a chance to test ride Oltre XR2 in 55).
And i feel it big a little bit. Also my fitter thought that i'll need 105 mm stem if i go for 55 and the reach is long if i go for 110.
And if i went for 53 i'll have to u use 30mm of spacers, so his opionion was that in that case front end wont be stiff enough.
Im wondering how many spacers u have under the stem of C60 and same question for Bianchi? Which headset cup u use on C60? Big or small? And what kind of stem?
And what is height and leg inseam? Im 175 cm, 82 leg inseam, using 110mm stem -7 deg, saddle height is 72.7 cm from the bottom bracket, and setback 52mm. Fort to add in this moment under the stem i have 12mm spacers, and using big headset cup.