You don't need two.
That said, the larger sized one has a wider radius cutting edge, which is more appropriate for larger nails, so better suited for cutting your toe nails.
If you can cut all of your nails with one comfortably, you don't really need two.
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The Party told you to reject the evidence of your eyes and ears. It was their final, most essential command.
If you're not careful, the newspapers will have you hating the people who are being oppressed, and loving the people who are doing the oppressing. —Malcolm X
Just a reminder: under international law, an occupying power has no right of self-defense, and those who are occupied have the right and duty to liberate themselves by any means possible.