Different species produce somewhat different flowers. The differences between varieties of the same species are likely to be subtle. With the newer hybrids, all bets are off, since they may resemble one parent or the other, or a combination of features, or something completely out there, depending on how the different genetics interact with each other.

I suppose they're both Cordyline for sure, are they, and one of them isnt a Phormium? Are they different varieties (like one purple, one green?)