We faced the same dilemma. After spending an afternoon with each of them we went for a manual 360 Spider. The 430 was a very fine car, and on paper represented a better buy. However, we much prefer the interior of the 360, it's softer exterior lines, and didn't notice the power difference in normal driving. In the end, the 360 "spoke" to us and the 430 didn't. Six years on, I'm glad we choose the 360 and would do so again given the same choice.
I think the driving experience is very different with a manual gearbox, much more envolving. To me it is not a matter of going fast, but rather having a special experience when driving.
I'd do the same that you did!