I think if you can get any 'extra benefits' from a room (that doesn't cost you more) then definitely go for that unit. For example, one might be slightly larger, be situated in a quieter corner of a hotel, have a better view, etc. Think about the end user ultimately. What would appeal to you more if you were staying there? I'd go and visit any site and get a real feel for the place and potential unit options.
I totally agree with the comments from @KGeeson because nothing beats actually seeing the investment you are buying as well as the area. By choosing the best room location, etc this may increase your annual income slightly but over a long period it can soon add up.
I agree with the above - however if you have a fixed return and exit strategy then it is less important. It also important to ensure that the hotel operates a good booking system to ensure that all rooms are booked in a good rotation
Exit strategy is also key for your decision, if you have a unit which has a better view or more useable space not only will this be better for the end nightly user occupation levels. But also should you look to sell the unit at any point, it will give you a better chance of securing the price you are looking for.
The contract terms will dictate the way returns are calculated and the actual room selection is only important if the room occupancy is dependant on returns to the investor. However if you have a choice then corner rooms, best views and top floors are always worth selecting.