Which NVME to use as my OS drive?

Motherboard: MSI B550 Gaming Edge Wifi

Current NVME: 2x 1TB Gen 3 (Crucial & ADATA)

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I'm upgrading one of my 1TB drives to a 4TB Patriot P400 V4 because I'm running out of space and its only a few bucks more than a 4TB SSD. The board only has 1 Gen 4 slot, so I might as well put the Gen 4 drive there. The real question is, do I use the faster, larger Gen 4 drive just for storage, or as a boot & storage drive. I know rule of thumb is to have your smaller drive for the OS and essential programs, but with the Gen 4 speed difference, does it even matter at this point?

While the PC was built for gaming, I have a lot of media and other software that I occasionally run. I'm thinking OS/games on the new drive and use the old drive(s) for everything else.