1.6 will have better resale value.
1.8 will have more driving pleasure.
I have driven a 1.6 and found it to be quite responsive. After facelift it has now got almost all the Essential features.
1.8 will give you Extra on top of what is present in 1.6. But whether that Extra is something you really need or can make a tradeoff, is a decision only you can take.
For example I found cruisecontrol as useless ( after driving a grande last year) given the kind of traffic we encounter on motorway now. You have to cancel it every now and then because people neither follow lanes nor keep distance while overtaking.