The Ruby is a "plush" road bike, so it's designed to be a bit more upright and stable, at the sacrifice of some speed. While I don't know anything about the Kuota, it might be a more aggressive bike, so it seems twitchy. (The biggest thing that helps with that is relaxing!) The gearing is probably different. While they may have the same number of gears (2x10, in all likelihood), the spread is probably different. The "plush"/endurance bikes tend to be geared lower, whereas your Kuota may be geared higher.

The good news? If you like the saddle on the Ruby, that's not a hard thing to buy.