Considering that firmwares on 4.1.0 and below can get hacks at some point in the future, you're better off getting a Switch from an actual retailer ASAP (since new Switch units are still below 5.0.0 since 5.0.0 was just recently released at the time of this writing) rather than somewhere from eBay where any seller can inflate the price. It's up to you in the end, really.
However, keep in mind that SciresM has said:
- 1.0.0 is the best firmware. If you're on 1.0.0, stay on 1.0.0. It will get public stuff via jamais vu on a timescale of [weeks].
- 2.0.0-3.0.0 are next-best, and are interchangeable. If you're on 2.0.0-2.3.0, feel free to update to 3.0.0 for homebrew (HBL launches next week!).
- 3.0.1-4.1.0 are interchangeable, and also good. If you're on them, *stay* on them. They'll get stuff later than 2.0.0-3.0.0, but are "safe" for custom firmware.