Hello Chris,
I had only flown the J170 until 2 weeks ago when I flew with my instructor in a J160 (mainly because I found a chunk missing out of the prop - Oh those pre flight inspections are actually important). With 2 up the difference is add 5kts to the J170 approach speed, takeoff etc for the 160. The 160 also has a little less aileron drag, so a little less rudder required to co-ord turns. When flying the 170 solo it sometimes feels like it could do with a little more impetus on approach but that is probably just getting used to having 85kgs less in the right seat. Appart from that they are pretty much the same.
I train at Wentworth with CFI Cliff Banks - Sun Centre Ultralights based in Swan Hill. Cliff trains at Wentworth Fri - Sun every F/Night.
Cheers Tim