i have flown both and find the J170 to be a pain in the bum for me. the J160 flies where you tell it and will land great for me, the J170 was designed to aid Novices to land a bit better which it does but this is the problem.... the J160 i can pick a point, hold the nose down, pull the power back whilst leveling off and she sits down nicely for me but the J170 will just keep going, going, going,going...... and going..... which i suppose is great for people who hold off to early like id did when i first started flying in an LSA, the J170 also slows the base leg down by 10Kts. i have found the J170 likes to cruise at full flap at 60KTS where as the J160 likes 70 Kts. i have had the J170 down to 50KTs (hope manny does not read this :) ) and it was as solid as a rock i thought i could even slow it down more but thought did not want to become another satistic. the J160 becomes very slugish at this speed for me.
i would buy a J160 if i bought one but if it was for a flying school a J170 is great, very forgiving.
just my observations having flown both..