Plastic intake here in weather ranging from +30 to -42 and no problems in 10 years.
That said, imho, 94,95 and 99-04 is the only choice.
94 and 95 you get the 205-220hp 5.0 (a lot of debate on actual hp numbers). The 5.0 is easily modded into making crazy power. Personally not a fan of the styling but you get the 5.0 instead of 4.6. Quite slow stock actually but modable into a beast.
96-98 convertibles are typically known as the slowest Mustangs ever built (second only to the Mustang II). Heavy and producing at best 215hp. Definitely known as the 'dogs' of the Mustang world. Modding starts off with replacing parts with 99-04 parts (PI intake) and then you hit the same modding scene as the 99+'s.
99-04 your looking at 260hp, pre 02 there's the plastic intake that some people worry about. Modding scene is decent now, best mod is a power adder like an SC.
Appearance is obviously a personal choice, interiors are practically identical... Though 96-98 there is a third 'pod' in the center console that contains a clock, as well i believe they stopped making the dual color interiors in 98.
... I've owned a Mustang of every generation except for 05+, so I don't have any qualms telling people how I feel about the various years. My dads 68 428CJ we worked on growing up will always be my pinnacle