That entirely depends on your filtration and such. I run a big oversized skimmer and large 20g fuge (I have a 80g but with a sump) and lots of fish with lots of food and rarely do water changes (I do about 10-15g) since the filtration mostly takes care of it.
They have plenty of sump tanks, any reason you don't want one?
If you like poop machines like tangs or foxface or want anthias that need to eat a lot... I would just get a sump system.
If your focus is more on coral and you just want a few fish then a AIO should be fine.
Most people always want more fish then they have room though.
