Since the Logix processors are 32 bit processors, it actually will slow down your logic computations to use 16 bit integers.  Make sure you use the DINT or double integer type as a minimum.  For instance when performing a math calculation using the 16 bit integer, the processor will have to add steps to convert the 16 bit integer to a 32 bit integer to perform the calculation.  When it achieves the result, it then needs to convert it back to the 16 bit integer to post the result.  In this example the 16 bit integer causes the processor to go through 2 additional conversions than would be necessary if a DINT type had been used.