This is a tough one.
Stevie was absolutely sublime on Mirage, contributing three very strong songs, but, she was the weakest by far on Tango. Minus Seven Wonders and her two lines on Little Lies, she only serves to bring Tango down. (Even though I have a bit of a soft spot for WISYA... if I'm feeling sad
)
Christine is brilliant on both albums, although Tango has Little Lies and Everywhere, which are possibly her two best songs, so Christine's Tango contributions have the edge on her Mirage contributions.
Lindsey's songs I find to be absolute dreck on Mirage, apart from Eyes Of The World, the same way Stevie's are on Tango, whilst on Tango he's brilliant and at the top of his game.
I prefer Stevie's contributions to Mirage more than any of the other material (minus Little Lies) but, as a whole, Tango is the better album. If only they'd put some better Stevie songs on there.