The tall rig mast is 2' taller, a few square feet more of sail area for both the main and jiob. There is also the bow sprit version adding more area to the jib. The tall rig and bow sprit versions are a little faster.
When racing C30's in one class, standard, tall rig and bow sprit together, seconds (time) are added or deducted to the finish time. Other factors such as 2 or 3 blade prop, fixed or folding, size of jib or genoa are also calculated to make all as close to equal as possible.