I am a long term user of Sonar too - and have finally lost patience with the team at Cakewalk. I love the workflow and the great audio facilities of Sonar, but the midi editing and the tempo map editing are absolutely woeful. I have repeatedly requested enhancements to these aspects of Sonar, but they really aren't interested. I use 8.5 at the moment, and will not go any further until they improve things. X1 is a joke - just a cosmetic upgrade at the moment, with no real fundamental improvements.
The score side of things don't bother me, as most DAWS are pretty rubbish at that when compared with Sibelius. I have started using Cubase 6, and it is far superior to Sonar in terms of its midi editing and tempo map flexiblity. I am finding some of the workflow a bit clunky - but that is probably me having to learn a new DAW. The expression map facility makes switching articulations in VSL a breeze - when you have worked out how it all works. I am looking forward to exploring Note expression too.....
I don't yet use Cubase in rewire mode - I tend to write in sibelius and export the midi. This works well on the whole, but you do need to be careful what you export if you want a 'clean' import to the DAW I am finding. Pauses, for instance, seem to cause havoc with the position of notes in bars in the DAW for example - and seems to cause real problems if the pause is in one part and not another......
I think you are right in your opinion of Sonar, and you can't go wrong with Cubase. If you are a teacher or student you can get a very good price on it too.....
My son will be starting a Music Tech BTEc in september where he will have to use Logic - so I guess I will have chance to see what Logic has to offer soon as well....