This is one of the most common points of confusion when people first put together an off-grid cooking setup, and it usually comes from treating the two as an either/or choice. They are not competing products — they are two halves of the same system. A portable stove is the burner: the metal unit with the flame control, pot supports and ignition that actually turns fuel into a controllable heat source. A gas canister is the fuel: a pressurised container of butane, or a butane-propane mix, that the stove draws from. Buy one without the other and you have a paperweight.
The reason it matters which you think about first is that the two have to be compatible, and that trips people up. A stove that takes a screw-thread canister will not work with a pierceable canister or a clip-on cartridge, and vice versa. So the sensible order is to choose the stove for how you will actually use it — a compact screw-on burner for a grab bag, a stable four-legged unit for cooking at home during a power cut — and then buy the canisters it is designed to take, plus a spare or two. The stove is the one-off purchase; canisters are the consumable you keep restocking through the season.