I went to find out more.
The 7280 about 0.2cm smaller in thickness / length / breath.
Weight for 7280, at 1.18kg, is 200g lesser than 5280
Material for 7280 is Magnesium alloy, whereas the 5280 is Carbon fibre
Battery life for 7280 will probably be slightly better than 5280, since it's i5.
Are these things worth the 1 year decrease in warranty?
Actually You can just get any model than request additional warranty which
can be done at additional cost.
Done that for my coy since Latitude series usually is three years only.
Than boss want another 2 years, we just pay for
extended warranty.
Provided that you talk to Dell directly, if through school/reseller
they may or may not have extended warranty.
Since they sell this SKU already means it is fixed cannot change.
If you talk to Dell directly, just remember to indicate that you are a student
than they will quote you using edu prices.
Hope this clarifies. PS I am not a Dell sales here.