CORTIS CLARK  Tiger's calculator is a nice improvement over previous calculators that have shipped with the system. It however isn't an expression calculator like iota-calc is, meaning you can't type in your expression as you would in code but rather have to break it down piece by piece to feed it in. To make that more powerful iota-calc has unlimited variables, and can remember expressions as well. iota-calc also has a debugger to help you see where your thinking has gone wrong with your expression. There are also quite a few niceties of iota-calc that Tiger's built-in calculator doesn't have. My favorites are the following: Mini-Calc mode to reduce screen real estate, the Ascii-Chart with annotations and type and find characters, Icon update in the dock so you can see your last answer, and being able to create an unlimited number of calculators. Of course there are many other improvements which you can read about in the feature overview.  
(Version 1.6)

CORTIS CLARK  Tiger's calculator is a nice improvement over previous calculators that have shipped with the system. It however isn't an expression calculator like iota-calc is, meaning you can't type in your expression as you would in code but rather have to break it down piece by piece to feed it in. To make that more powerful iota-calc has unlimited variables, and can remember expressions as well. iota-calc also has a debugger to help you see where your thinking has gone wrong with your expression. There are also quite a few niceties of iota-calc that Tiger's built-in calculator doesn't have. My favorites are the following: the Ascii-Chart with annotations and type and find characters, Icon update in the dock so you can see your last answer, and being able to create an unlimited number of calculators. Of course there are many other improvements which you can read about in the feature overview.  
(Version 1.5.5)