You mean, High Step Challenge vs. High Step Circuit? I'm a little dense tonight. LOL If that's what you mean, HSChallenge is a fairly big step up in intensity from HSCircuit. Circuit is slower paced and the various intervals are shorter. In other words, it's easier.
Challenge is much faster paced, there is little break between exercises (which are tougher) and the intervals (especially the cardios) are longer. It's higher impact, too.