In the end a toy car is all about what appeals to you and SWMBO. The Lotus is definitely more hard core than the MX5 but the Caterham is worse still so I cant see that appealing to your wife. I'm not even sure I would call it a car. Of the two MX5 variants, its a personal choice.
I have never been impressed by FIAT quality and even on the Ferrari the build was such that exhaust manifolds are a 20k mile consumeable ( seriously!) at £5k a pop and clutches on the F1 boat are 10km to 20km items at only £3k a pop. The FIAT saloon that I bought my son was a rolling disaster with so many major faults you wouldnt believe. So my choice every day would be the Japanese built car.
If reliability is the issue then yes, the 100% japanes MX5 is the safest bet. About them all being toy cars, that's true I guess, none of them will ever be neither a family car nor a "seriously fast" supercar.
The logic behind the short list I posted, from the Caterham to the Lotus is that of someone looking for a "fun affordable car". And reliable, preferably. I hear you on your son's Fiat or the Ferrari's 20K mile exhaust manifolds, but I can raise you with my own M3W and its 2K mile exhausts. I just wouldn't call my Brooklands - the only M3W that can have more problems than a ... normal M3W - a rolling disaster because I can't get over the love I have for that under-engineered piece of ... kit.
And the Caterham was originally put into that list precisely because at some point I started to wonder if I should keep or sell the M3W. The little 165 might be a suitable replacement for a more extreme experience. However, in the end, I decided to keep the M3W, so the Caterham fell out of contention for my next fun car.
And decidedly I need something that is both:
a) somewhat unique - that rules out the Mazda;
b) different from the Plus 4;
c) different from the M3W - that rules out the Caterham;
d) affordable;
e) fun
So, only the Lotus and the Abarth fit this set of criteria. The Lotus is a bit more extreme, and expensive, the Abarth a bit more "bourgeois" if you like, but not so much that you won't feel pleasure when driving it (not a taxi to go from "A" to "B").
Both have character. Both are "head turners". Both will lose value at a much lower rate than regular cars. And if any of them is a possible rolling disaster (something I doubt), I guess by now I'm a veteran in that department so I'm not too scared!
