Look at the footnotes of the ASCE table. Those modify the table values to give you the at-rest pressure. With that you get rough agreement between the tables. As for the variance between the nominal active values, both of these documents are consensus standards of two different bodies. Its all about what the specific group can agree on. I would not worry too much about the differences for several reasons: 1) It is impropbable the exam will ask you to pull one of these values out. 2) if it does ask you to pull out a value, it will tell you which standard to use, 3) if in the unlikely situtaiton you are asked to produce a value for a worked problem and they dont give you the basis document to use, so long as you document your source you will get credit, 4) When it comes to real practice any significant wall is likely to use values from a soils report where a geotechnical engineer has worked out what the pressures should be based on the actual soils and soil mechanics.

Robert Hale, PE, SE