The 6150 is a "fixed alpha" keypad. That is it will display only the few words that are built into its LCD display (alarm, away, chime, AC, bat . . . ). As an operational keypad, there is nothing wrong with it.
The 6160 is a "full alpha" display. Custom labels for zones can be programmed (front door; west bedroom window; down hall motion. . .). Additionally, depending on the panel you have the 6160 can display the event log and the time. The big benefit is programming. Virtually all Ademco/Honeywell products require the use of an alpha keypad to program zones; it can be done without, but it is extremely difficult and not recommended.
Both keypads have a built in transmitter and receiver for wireless expansion (the RF part).
Hope this helps.