Reading the notes of each fragrance, they really are quite different--though not completely dissimilar in the final result. I think they're both bottle worthy, but if I had to choose only one, it would be Versace Man Eau Fraiche. This is because I like the slightly coniferous smell to the Versace fragrance.
I own VMEF, and my girlfriend owns Light Blue. I've been known to use a spray or two of her Light Blue.