Both formats are the same medical-grade silicone — the difference is just shape, and shape matters more than it sounds like it should.
Pre-cut sheets are sized for a standard C-section incision: one shape, ready to apply, no cutting or measuring. If your scar is a fairly straight horizontal line at the standard height, a sheet will usually cover it edge to edge without you doing anything.
The tape roll exists for everything a pre-cut sheet doesn't fit well — a scar that curves, one that's longer or shorter than average, a revision scar, an older scar on a joint, or a scar in an unusual position. You cut exactly the length you need, so there's no overhang and no gap.
A simple way to decide: lay a ruler along your scar. If it's close to a straight 20cm line, sheets are the easier day-to-day option. If it curves, sits somewhere non-standard, or you're treating more than one area, the roll gives you more control over the fit.
Some people end up using both — sheets for the main line, tape for a smaller area elsewhere. Either way, the material and how it works is identical; you're only choosing the shape that matches your scar.
Which one actually goes further
It depends less on price per unit than on how much of it you actually use. A pre-cut sheet that fits your scar edge to edge wastes nothing, so a 10-pack covers 10 full applications. A roll is more economical when a sheet would leave you cutting off and discarding excess on every single change — over weeks of recovery, that offcut adds up. If your scar is close to standard length, sheets are usually the better value as well as the easier routine; if you'd be trimming a sheet down every time, the roll stops that waste and works out more efficient over the same stretch of recovery.
See both side by side: Scar Strips (10-Pack) and the Scar Tape Roll.
Related reading: When can you start using silicone scar sheets after a C-section? · Showering and sleeping with C-section scar strips: a practical guide