The difference is access and range.
Dial test indicators are good for indicating vises, aligning the edge of a workpiece, finding the center of a small hole, centering a part on the lathe, etc. They are versatile and easy to get into tight places, but they have limited range.
Dial indicators can have a much greater range and are good as carriage stops on the lathe and for comparing the height of parts on a surface plate, but they are big and bulky and therefore work better for dedicated applications.
Tom