Go with the Mercon ATF as recommended in your owners manual.
Most places I've found don't carry the Motorcraft Mercon; might be a good idea to order it online somewhere or specifically ask for it specifically (by part number) at your dealership. Will be worth the price IMO.
From our 2007 owners manual (pg 218)
Power steering fluid: Motorcraft MERCON ATF
Part Number: XT-2-QDX
2012 Fusion SE 3.0L V6
'86 XR4Ti ; 2.3L Turbo, 15psi
1988 F150 Custom
'07 ST ; formally bewst'd - R.I.P
D23 Crew: #07