I'd say Mitsubishi, from reading here, is superb in handling warranty issues. They have replaced heater cores that entail tearing apart the entire dash, short blocks for piston slap, countless rear axles, and many other defects that I suspect other manufacturers would try to weasel out of.
I'm particularily interested in the first claims to surface for rusting issues. There's a lot of bare steel in our little cars, the paint is fairly thin in spots and whatever rust proofing is factory applied is invisible to me. It doesn't really matter how good the mechanical warranty is if the unibody starts to resemble swiss cheese.
Oh, and I've rented the Versa & Mirage back to back several times and found the Mirage to be the better car. On the hwy the Versa turned about 1600rpm@70mph (lowest I've personally seen at that speed) vs. the Mirage turning about 2000 for the same speed. Considering the volumetric difference of the engines the mpg difference is explained pretty well.