The 348 had many drivetrain problems that Ferrari handled under warranty, but not all cars have had the updates. I'd drive a 355 over one of those any day...the 355 is a more advanced driver's car anyways, has all the updates, a better engine, and a stiffer body.
Yes, I'd choose the XKR. A coupe, not a convertible, with the reduction supercharger pulley. I've driven several XKRs, with and without performance modifications, and I love the way they handle. Plus, there's more aftermarket tuning accessories, available for cheaper, for the XKR.
I like to have fun with my cars.