I honestly prefer the Freedom. Haven't seen Destiny yet, but I absolutely hated SEED.
Freedom over Strike Freedom, of course, but Destiny is horrible. It's written by the wife of the guy who wrote SEED. It's a giant lovestory with weird ass animation and an overall boring plotline. I loved the designs that came from SEED, though. Strike is easily one of my favorite gundams. It portrays the modern gundam appearance almost completely, in my opinion.