i'm thinking of getting an oscar but i heard they are really messy and i should go barebottom.
i don't think the bottom will be visible but if the bottom walls are scratched, then it might not look good..
if glass is scratched on the inside of the tank, as soon as you fill it with water, the scratches will disappear....as long as it's only scratched on the inside, it shouldn't matter at all really.
The severity will depend on how you or the previous owner takes it out of the tank.
I have scratched up the bottom of some of my tanks fairly bad by uncarefully scooping it out of my tank. However when full of water the majority of them will not be seen.