I'm in your very comfortable shoes, or at least I used to be.
Preface: Ultimately, this is a personal decision, and comes down to the man doing the driving. Also, either choice will result in an epic car.
I would agree that 360 depreciation will be very minimal for the foreseeable future. I also agree that F430's have a little way to go down before they get flat like the 360.
For me, the price delta between the 360 and the F430 I want is less than $30k, more like $10-$15k. So, I'm going for the F430 for multiple reasons:
1. Was planning to get an F430 anyway, on the way to a 458 Spider. It's cheaper to get one of these cars instead of two.
2. Maintenance costs on the F430 tend to be lower, and over the course of my term, I'll come out ahead (theoretically).
3. The F430 is a reasonable enough advance / evolution over the 360 that the incremental cost increase is worth it to me.
4. My wife likes the F430 better than the 360. She'll be more likely to enjoy it with me, which is important to me.
There are probably other reasons. If your term is as short as I seem to recall (you were looking at a 1 year term) then you'll probably lose less money with a 360 than you will with an F430.
Again, it's a personal decision. Ideally, you would get some seat time behind both to help make your decision.
Most people say: "If you can afford the F430, get the F430 instead of the 360." There are some exceptions to this - it's not the rule, since it's a personal thing. Again, either way, you're in for a sweet ride.