The difference in these detergents is in the amount of suds they produce. With a front loader, for a given detergent, the slapping and tumbling action will produce more suds than will a top-loader, where the clothes are submerged in the water. So - front loader, low suds detergent. Top loader, high suds detergent. All this means a front loader detergent won't cause you any problems if it's used in a top loader machine. That said, the bubbles help the cleaning process by dislodging dirt from the fibres, so your clothes may not come out as clean as you'd like.