The verdict
If most of your work is social posts, ads and visual assets, with the occasional deck, pick Canva. The free plan is generous and the speed from idea to finished asset is hard to beat.
If your work is sales decks, board packs and reports that travel as files, or you already pay for Microsoft 365, pick PowerPoint.
These tools sit together better than they compete. Many teams make visuals in Canva and place them in a PowerPoint master deck. If you can only pick one, ask what leaves the building most often. Posts and ads point to Canva. Decks and proposals point to PowerPoint.