Transformation from NAD1983 to WGS1984

 The best one to use is : 

NAD_1983_To_WGS_1984_5

    See the details of other transformations:

   

NAD_1983_To_WGS_1984_1 – for the entire North American continent.

    NAD_1983_To_WGS_1984_2 – for the Aleutian islands.

    NAD_1983_To_WGS_1984_3 – for Hawai’i.

    NAD_1983_To_WGS_1984_4 – superseded by _5; this transformation method should no longer be used!

    NAD_1983_To_WGS_1984_5 – for the 48 contiguous United States.

    NAD_1983_To_WGS_1984_6 – for the Canadian province of Quebec.

    NAD_1983_To_WGS_1984_7 – for the Canadian province of Saskatchewan.

    NAD_1983_To_WGS_1984_8 – for the Canadian province of Alberta.

More about Geographic Transformations :

ESRI Blog Post: About geographic transformations and how to choose the right one

ESRI KB-Determine which NAD_1983_To_WGS_1984 transformation to use(Old Document –but relevant)