When buying toilets from displays at a home center, etc., you can visualize how big of a "water spot" the bowl will have by visualizing the weir or overflow line on the trap remembering that it flows over the lower part of the peak of the trap opening at the back of the toilet. Some of the newer water closet bowls play around with how narrow or wide the hole is at the bottom to affect the size of the water spot so the same amount of water in the bowl could have a bigger and shallow or a smaller and deeper water spot.