The Grand is central, central, whereas the DT is a bit off centre, by the English Park, but not by very much. The Grand has a long history as Yerevan's oldest hotel (and its own Wiki page!). So I think you're paying for location and prestige, it's not really a typical SLH property in my view. Yerevan is a inexpensive city so your DT rate seems high (and The Grand a bit high). But my speculation is that both hotels will have extensive breakfast buffets since (a) the cost of food is a lot lower and (b) the quality of fresh items such as eggs and salads will typically be greater than Western supply chains - so it's easier as well as cheaper to please guests.