I’ve been searching the Internet for reviews and discussions. The original developers of Sibelius went off and created Dorico and reportedly honed the latter based on lessons learned from Sibelius. So much to choose from!!!

Both Sibelius & Dorico have free starter versions, so he can try both of these in addition to MuseScore. I’ll get the most comprehensive product for whichever one he likes best. He has a couple of unfinished compositions (limited by Flat), so he can use these as a specific task/test to evaluate & compare all three programs. Thanks everyone!