Chance are exactly same, unless some internal desigh have some kind of prefilter sponge or something, but then you need to clean that, and pump can overheat if not enough water flow to it etc.
There is more maintence with internal pump designs, because you need to take pump out of body to clean it and such designs are only made to save space, nothing else, and beside more maintence they are actually a less efficent than models with external pump because less contact space inside it.
-Today we have many new kinds of filtration like fleece rollers, compact ats and algae reactors etc, and as well a powerfull but (relatively) small skimmer pumps, so all that contribute to production of smaller and more compact models