My wife & I currently own a 159 Ti 2.2 JTS and a 159 Lusso 1.9JTDm (re-mapped). If I had to choose one in the morning, it would be the diesel Lusso spec.
The Ti suspension is hard and unstable over bad roads, the 19" rubber is expensive, the 2.2 engine is thirsty and not particularly powerful. Braking performance is really no different in everyday life. The 1.9 engine seems (to me) to be more usable than the 2.2 petrol.
I do like the 2.2 on a track or a spin with the AO club out and about
But every day living the 1.9JTDm, for me, would be the way to go.
When the diesel is warmed up (again my opinion) you'd be hard pressed to hear it when driving on motorways or B-roads.
From the outside the Ti is a better looking car on 19's.. no argument there.
On the inside, the Ti has electric seats and Blue&Me, our Lusso doesn't. The Lusso has the Bose sound system, the Ti didn't. They are both have comfy leather, climate control. Both dashboards are made of metal etc.
We had both cars side to side on a private road as an experiment, and there was not much in it. The diesel seemed to get off the line quicker but the petrol pulled ahead after. Drivers swopped cars and same result.
The ideal version, for me, would be the Ti spec on 18" with the 1.9JTDm, re-mapped.
DISCLAIMER: I have not driven the 2.4 nor the 2.0. diesels.