I'm not an advanced user of S1, but for a couple days of getting to know this daw I've seen clicks that disappeared after changing the asio buffer, and strange behavior when midi editing (for example, click+shift works well only if you press shift after clicking. if you press the first one, the note will not be set.), and a constant cursor lag after clicking into the working field, in Sonar it happens instantly. Add here a huge number of interface elements, from which it is dazzling in the eyes and the impossibility of changing the appearance...
Not all of this relates directly to performance, but is directly related to the performance efficiency in comparison with the Sonar. By many factors this gives way to Sonar. And who only says that they are very similar? These are two different universes.
Whatever your choice, I strongly recommend that you pre-test the demo version.