Confusion with the relation between SNR, voltage divider and amplifier concepts
With a signal that is ten times larger, the quantisation noise from the ADC will be about ten times lower. On the other hand, if the x10 amplifier has an error of 2% then you will have to factor this into the bigger picture because it may represent a more significant error than just ADC quantisation noise. Amplifiers may not be perfect spectrally either so again, it's another error to consider. Amplifiers can also produce offset voltages that add an error.

In short, the most appropriate measures are specific to the application and generalisations are just that.