There are as many right answers as there are musicians! This is a tough question to answer but is best addressed with questions themselves. huh? Yes, ask yourself these questions to narrow down your search.
First, we can cut your search in half with these:
Do you need to be portable? Are you a DJ or Electronic Musician that will use it for performing? Are you a member of a band and would like to to record live gigs? Do you want to use it for management and your Point of Sale for Merch? Yes to any of these will make you lean towards portables.
If you are staying put, how much power do you need? Desktop machines are able to pack a lot more power simply because they have more room to pack more parts. There is also much more room to upgrade. With that said, this doesn’t mean a desktops can’t be portable, there are plenty of people who find ways to cart a fully packed recording rig and video rig to live shows. There are racks and cases built to do such a thing. It all depends on the balance between true needs and budget.
Now, once you have made this decision, you then need to look at the different levels of Macs available in portables and desktops then match the model with the system requirements of the applications and peripherals that you wish to use.
So, Here are some links to get you started. I will add more info for time to time…..