eslHQ - sitting/seated

Both are correct, but "seated" is more formal. In normal everyday conversation, and informal or neutral written style, we'd use "sitting".

If you feed them into a concordancer - I used the Cobuild concordancer - you'll see that the examples that come up for seated are all from formal written English, for example :

Ensure the casualty is seated or lying down whilst being treated.
... has the necessary space for those seated, whilst retaining an interesting appearance.
... such as one of Josef's dreams. Fat lawyers seated stuffing themselves, urging him to eat at the ..
...of the British Defence Minister, Mr Tom King seated behind a model of one of the tanks which is ..

whereas for sitting, while there are still plenty of written examples, spoken examples come up too :

I mean I know somebody who's you know sitting in a wheelchair after a spinal injury thirty
That's what your dad says isn't it we were sitting in the car and she lent over and a fag fell
I'd have a conversation and he'd be sitting on the settee and I'd be having a
Easy for Warrington. Andy from where you're sitting what a great game Gary Pallister's having