Both designs are pretty attractive, but we're sure plenty of people will prefer one over the other. Either way, we're really digging the look of the Excalibur class vessel. It makes us wonder what other old designs will feature newer updated versions as well, such as the Klingon Empire's Bird of Prey.
Having both the original and updated appearances of ships would be the wisest choice, of course. Although we're not entirely certain many players would want to enter a fight with the original Constitution class version of this design, as that one's a bit... outdated.