I think it's piggy preference
I know the rule of thumb is the greener the better. I have lots of different types of hay. This is my set up.
I use cheap standard hay for their hay tubs (basically two shallow plastic containers - almost like a cat litter tray) to line the bottom and the back where they tend to do their toilet.
Layered on top of the cheap stuff is the more middle range stuff - I have a Timothy hay with apple and carrot - at the moment.
Hanging above their hay tub is the posh stuff in hay balls - I use a chamomile hay - they LOVE it and it's meant to help calm them - the same way a nice cup of chamomile tea would have on us I guess.
I think it's nice to mix the hay up a bit. You'll soon figure out which one they like the most - but it just makes for more interesting and varied nibbling. And they will eat all of it, even the cheap stuff.
But mine wheek in excitement for their evening fresh chamomile hay more so then they do for their veggies! They aren't ever without it - they have a constant supply of fresh hay every day in their hay balls and I change the hay tubs every other day.
But I'd deffo get a cheap one for the bottom of their hutch/cage/tray tub, on top of that layer it with the medium expensive/quality hay - (I refresh this inbetween clean outs - just spread another layer of fresh hay on top everyday) and then a really good quality hay in their hay rack/ball.
That way you know they are getting the goodness of the best one and your money literally is being wee'd away......hehe.