It's better to talk milimeters here. According to some older posts about 0.2 is what makes diamodns 'different' side by side. I'd need more than that to say 'this is bigger' between two set stones (different rings, sure that): probably about 1mm, esp. if the settings are different.
Ana's right. You can have a heavy stone with a thick girdle and a small table, but have the same "carat weight" on another stone look much larger.
For instance my stone is a 1.73. It has a larger table than most. I saw it compared to a 2.02 radiant in a store window and the table was so small with a HUGE pavillion depth that gave it the WEIGHT, but not the SIZE...