Any reason to move it or not?
1) If you move your 401k to your Roth IRA, that is a taxable event. Depending on your age and retirement status, that may not be something you want to do right now
2) If you have a tIRA, moving your 401k to a tIRA will not be a taxable event. However, it would complicate a future backdoor Roth conversion if you need to do it.
3) If you fund options at Fidelity are good or comparable to Vanguards, why do you want to rollover the account? You should still be able to buy, trade, sell the funds in your fidelity 401k, even though you don't work for the old company anymore. The only thing you wouldn't be able to do anymore to contribute to the account.