I've always found this interesting. IIRC the events of Star Trek V occurred in 2287, with VI coming in 2293. A pretty significant gap.
Do we have any idea of what the Enterprise's mission was like in those years? Did they do another 5-year type mission of exploration? Or were the ship's functions more ceremonial (ferrying of diplomats, etc). I would imagine a fair amount of Starfleet command still has issues with Kirk's insubordination, considering the end of ST6. Maybe that played a role in giving him a junker ship, maybe they were given all the crap missions too.
Despite that, we're not really presented with the idea that the E-A is just a pale imitation of the original by ST6. Did the EA have a time to build its own legacy?
You might conclude that there has been a military buildup in the intervening years given the differences in the ship. Obviously the bridge was much different and more militaristic-looking, and you have crewmen sleeping in bunk beds which suggests there were a lot of people on board. But then again the Excelsior is the most advanced ship they have and it's off on a survey mission forever far away from Starfleet.
Just a lot of missing gaps and inconsistencies between the two movies. In the real world I would imagine that's more a function of the studio/writer/director having much different visions for each movie. Similar to the gap between TMP and Wrath of Khan, which I find pretty interesting as well.