Scratches on the inside tend to be far less noticeable when the tank is filled with water, because water and acrylic have the same index of refraction.
They'll tend to collect algae, because most acrylic-safe algae scrubbers are too rigid and coarse to effectively clean within scratches. But an Original Mr. Clean Magic eraser (other varieties have additives) will do the trick quite easily.
Scratches on the outside are a different matter. I have the Novus kit. Haven't tried it on an aquarium yet, but have used it to remove scratches from other plastic items, and it did a good job.