Hi,
The hay cubes are better than no hay but they are a mere shadow of what real hay does. It's most likely not the hay but the dust. Low quality hay is often dusty. You should offer your rabbit a variety of hay....all the grass hays such as timothy, orchard grass, brome, oat, bermuda, etc. have basically the same nutritional value. Offering a variety of cuts in a "buffet" encourages a more natural foraging type feeding and gives them something to do. Since hay is the primary method in which the teeth are worn down, offering differing types of hay requires differing chewing mechanics and wears the teeth down better. And there is no need to avoid alfalfa. The concern has always been the calcium levels and it's alleged relationship to bladder sludge. It appears that view isn't totally accurate. However, alfalfa does have a higher calorie content and can lead to some weight issues. But alfalfa hay is better than no hay at all. We do offer it as a treat on special days such as holidays and anniversary dates.
If you could put you general location in your profile...I have excellent hay providers all over the US with really dust free hay....and I have really bad allergies. I'm sure other forum members can also refer you to good quality low dust hay.
But to directly answer you, while hay cubes are certainly better than no hay, they do not equal the benefits of loose hay.
Randy