The powder is awful, but supposedly better for you (more easily assimilated or something like that.)
A few years back I was taking a green food product that was in powder form and had a lot of spirulina in it. The only way I could get it down was to mix it with grape juice. That helped, but it still was an awful experience. Needless to say I didn't take that stuff for very long.
Go with the capsules or tablets. You want this to be fun, not a chore.