They are fine if they eat them, some chins won't touch them and you will need loose hay. I personally would not feed just cubes, loose hay is important IMO for good dental health.
I've heard both sides, but do prefer to give both, but loose hay is their main source, but I'm a little strange, as I find it relaxing to clean up after the lil buggers!
I free freed loose hay and will toss in a cube as a treat. However, new girls hate hay cubes. They toss them around and pee on them. Shelly is the only chin that gets cubes now.
my boys get loose hay as well as cubes. they are in a phase where they prefer loose hay these days, but i still give them the cubes for variety.
drilling holes in hay cubes and putting them on hanging toys saves them from getting peed on! i find it also increases Rhino's interest in cubes. Guss nibbles on cubes more when they are just loose on his favourite shelf by his hammock.
I use loose. Mainly because two of my brats won't touch the hay cubes. I've been meaning to take what I have and drill holes in them so I can use them as toys. I THINK they'd go for them then...