They are not as big as the PPEs, but their purple centers appear slightly darker. Interestingly, they take on a slightly different look under T5s. The photo is of them under MHs. The main difference, I think, is that when they're under T5s the skirts become longer and more separated.
They definitely do grow well for me... it seems like I have a new one every week in my T5 tank.
Are zoos better under T5 or MH or VHO? Mine I think does better on MH.