Did one of these days a year or so ago. Had a go in an Aston DB9, Lamborghini Giardo (sp?), which is basically an R8, and a Ferrai 575.
The Lambo was the most confidence inspiring (4wd, and it was wet that day) but I had the most fun in the Ferrai. If I was buying one it would be the Lambo, if I could do one more lap I'd take the Ferrari.
It's odd but my ascending order of preference is Aston, Lambo, Ferrari which is also the order I drove them in. Maybe as I got to know the track I was having more fun and the last car would have been best whichever it was?
Of yours, 355 no question. Maybe pay the extra £15 anyway if they'll let you do more laps, it just gets better as you practice.