B..
Just being really honest, there is NO competitive software to Photoshop. It does not exist. Photoshop, is the best. Many people might not like it, because there is a lot to learn. If you don't know how to use it, Photoshop can feel pointless. If you take the time to learn it, there is nothing you can't do with Photoshop. With every other software out there, it will have so many things Photoshop can't do. Adobe Lightroom is also good. It's less expensive, less intensive, and I've known photographers with small businesses who love it.
P.S.
S H. makes a great point! Macs are most definitely the best for any kind of editing.