Remember, in-pond filters work, but they may require a lot of extra maintenance. Outside filters are generally recommended and provide a better filtration process. 

Your choice of a waterfall type filter or a presurrized system is up to you. The nice thing about the new presurrized system is that many models have a powerclean or backwash feature requiring less maintenance.

The main issue to remember is that you must match the right pump to that filter for proper operation. If you want more GPH then is recommended, you can always use a flow control.