For most workloads, the honest answer is that it matters less than people expect. Pick something current, widely used, and that you or someone in your team already knows.
- A mainstream long-term-support Linux distribution is the safest default — the largest body of documentation and the widest package availability.
- Match whatever your deployment tooling or guides assume, so you are not translating instructions.
- Prefer a current release over an older one. Running an unsupported version to avoid a migration is a decision you pay for later.
- A minimal server install is preferable to a desktop image — less memory used and less attack surface.
Reinstalling
Reinstalls wipe the instance completely. Take your data off first, and treat a reinstall as a clean start rather than a repair.