Map value is a decision making technique while DT is used to set the properties.

Map values has a Row-Column structure and returns a value while DT doesn't return any particular value.

Use a map value to create a table of number, text, or date ranges that converts one or two input values, such as latitude and longitude numbers, into a calculated result value, such as a city name. Map value rules greatly simplify decisions based on ranges of one or two inputs. Use a map value to record decisions based on one or two ranges of an input value. A map value uses a one- or two-dimensional table to derive a result.

Use a data transform to define how to take source data values — data that is in one format and class — and turn them into data of another format and class (the "destination" or "target").In general, data transformation involves both mapping data from a source to a target, and performing any conversions or other transformations on that data that might be required to achieve the intended mapped results.