Nigel,

The most user friendly program was Encore (which went out of business but you can still get a copy from GVox. It's a great sketch pad and I'm not sure they upgraded their graphics so that it's as good as Sibelius but it has one great usable feature. You can
print up a part, play it back, rehearse with it and then score what you've rehearsed.
To some degree you can do this with Sibelius by just selecting the line you want played by itself and rehearse with it but Encore does this easier with the flick of a space bar. I wish
all the programs had that feature.

Sibelius does export to Logic Pro. MIDI files are easy to load. I've composed for example jazz solos and exported them to Logic along with my Band In A Box files. Sometimes I mix in my BIAB with Sibelius arrangements that I've done onto Logic. BIAB sounds pretty good on Logic. You can update BIAB with digital sounds (the more expensive model) but really when converted to Logic, you can get whatever sound you want.