The choice between external and internal filters depends on various factors. External filters like canister filters generally offer higher filtration capacity, larger media volume, and customizable options. They are suitable for larger aquariums and can handle heavy bioloads. Internal filters are more compact and can be discreetly placed inside the tank. They are suitable for smaller aquariums and provide sufficient filtration for moderate bioloads. Assess your specific needs and tank requirements to determine which type of filter is better for you.