The Vengeance is 1400+ meters long, has a variety of firepower and actually WORKS.
Same cant be said about the tiny little Excelsior which did squat in ST3 and ST6, and served as cannon fodder in many of the pointless battles in DS9.
ST3: Sabotaged by Scotty. Not representative of the class.
ST6: Survived the Chang fight with no significant damage (unlike the Enterprise
). Performed well here.
DS9: Outclassed by 80 years of technical innovation. Not fair to hold against the class at its debut.
So, the only instance we see the Excelsior
-class at its peak, it outperforms the Constitution
class. Sounds a lot like the Vengeance