imo (which might not count for much going by my previous car history) it all depends on what you want out of the car.
id say go for the 160, but only because i dont see the tf as being a 'sensible' car, so might as well go for the most powerful. if you are worried about fuel consumption or insurance then look at the 1.6, but then you lose out on features standard on the 160, eg. the wheels, brakes, central locking, leather/half leather seats (although all of these were options and a previous owner might have added them on later down the line, so you can find 1.6s with all or most of those).
two choices out of the 1.8, the 135 and the 160.
the 135 is more to tax, and on paper, fuel consumption is worse (dunno how true that is in real life).
however, when i looked to buy, the 135 models are generally easier to find, usually in better condition/lower mileage, and cheaper to buy.
as you are asking, you probably dont mind either way (for me, it was the 160 or nothing), so find one you like the look of in terms of colour, spec, mileage etc, and give it a look over.