I've stayed at both "airport" hotels and can say that the one within walking distance of the airport is decent despite a shabby exterior. As with other european hotels be aware that a single and double room contain twin beds, not so good if you want to cozy up with your wife or g/f. My preference is the "luxury suite" which is about the size of an American hotel room.
The other hotel is located in Borispil town about a 10 minute taxi ride from the airport. It is newer but the interiors are about the same.
The Borispil hotel is slightly cheaper but when you add the round trip taxi ride it evens out.
The airport hotel has a decent restaurant attached to it, it's not as good as the ones in Kyiv but it's not bad either. Borispil hotel has a "cafe" inside where they cook a limited number of dishes/items mainly reheated style fair.
Both hotels feature continental breakfasts that are ok.
The airport hotel can fill up during the summer so if you think you will need to spend a night there reserve early. Otherwise you end up sleeping in the terminal or having to get up an extra hour or so early to ride the bus/taxi to the airport from the city.
Directions: Exiting the terminal walk past the buses to the main road leaving the airport. The hotel is about 3-4 blocks down on your right. Beware ice in the winter and the sidewalk conditions can weaken your luggage.