The XP1000SSS is rated for 125 gallons while the 160INT is rated for 200 gallons.
The XP1000SSS runs on a Bubble Blaster 1000 pump while the 160INT runs on an Aquatrance 2000 pump.
The 160INT is a little taller of a skimmer but it does allow you to run it a little deeper. The XP1000SSS needs to run on 5.5" of water while the 160INT should run in 8-9.5" of water.
The 160INT is rated for larger tanks because of it's neck size. The 160INT has a 4" neck while the XP1000SSS only has a 3" neck.
Hope this helps...