I'm looking to buy either a used 147 or GT and I'm interested in opinions on their handling.
will you be considering like for like? for example, both 2L models or both JTD's or both V6? whilst they'll still be different, they'll be more similar than comparing different-engined cars, which may be chalk and cheese, not only for power-delivery reasons, but also front-end weight.
as mentioned, 147 is short wheel base derivative of GT/156. ( @ cul: brera is also short wheel base derivative of 159.) so the chassis designs are very similar between 147 and GT, including suspension design (ie: front double-A arm (wishbone) + rear multilink strut). yet the shorter wheelbase of the 147 theoretically makes it 'more chuckable' and nimble, at the expense of being 'choppy' over bumps. IF both cars shared exactly the same suspension setups, i don't think there'd be much difference. however, the suspension 'tune' is
my experiences with 147's have been quite limited, to loan cars when mine is being serviced. overall, the 147 is good, but i think the seating position was a bit higher, which loses some of the 'sporty' feel of the GT, which also has quite a high window sill line for a cocooned feel. i've driven only 2L TS versions, and they haven't absorbed small bumps too well, with a crashy sensation; yet this may have reflected worn dampers as much as anything. GT - albeit mine a V6 - feels more refined; but i will say, the turn-in of the heavy V6 is not as good as a lighter 4cyl TS.
i don't think there's a straight answer, and still depends on the engine choices. i suppose you need to testdrive to find out what you prefer. i personally love the GT.