Used them a couple of years ago but have never used either pasture nuts or pony cubes so can't really make a comparison. They were palatable and non heating if that is any good. Best thing is maybe to compare their nutritional value as listed in the websites for each manufacturer, could give you a reference point to start..
I've used them, one of the few things that don't heat my mare up. They were recomended to me by a show jumping trainer while my mare was with her she started her on these. They smell lovely. I would use them over pony nuts if I could but the nearest supplier is too far from us to make it viable.