To be honest I'd buy them both.
I just did something similar to prevent a competitor from grabbing a name that was almost identical to the one I'm developing. I'm just going to redirect that site to my developed one.
Oh wait, you're asking which one would SEO better?
Alright, if it were me, I would do AsiaHotels.com if you were doing a service to help people book hotels in Asia.
AsianHotels sounds like it would be a study on the architecture of hotels in asia or something.
AsiaHotels would be better for SEO for search terms like "hotels in asia."
No one wanting to travel to Asia is going to search for "asian hotels." That'd be like if you were going to Germany, would you search for "Hotels in Germany" or would you search for "German hotels"?
Exactly.
edit - just saw you said you're not a native English speaker.
AsiaHotels - if you're doing a hotel booking webpage
AsianHotels - if you're doing a study on the hotels themselves.
Both - if you can afford it