The Excelsior II was built as a varaint of the Excelsior Testbed, made to be the 'regular' Excelsior, and would be mass-produced. The first two ships of the class, USS Enterprise-B and USS Kongo, both suffered problems with their impulse engines and computers, so much that Starfleet decided to cancel the Excelsior II project, leaving the other unbuilt hulls to become regular Excelsiors, which was found to be more stable. Then, around 2330, Starfleet needed some medium-sized explorers that could be quickly built, so they quickly dug up the design for the Excelsior IIs, and built 5 more ships of this design, with the Lakota being in this group. These ships also were improved in that the safety problems of before were corrected.

Sound good?

At any rate, here's my two cents regarding the Excelsior.

Assume for a minute that the Enterprise B had a mission similar to the rest of the Enterprises, deep space exploration. Perhaps the refit Excelsior was better suited for such missions. (More sensors, science labs, what have you.) If so, perhaps the Excelsior refit shared the same fate as other Explorer type vessels. These ships are assigned to the wild and wooly areas of space, and often suffer for it. Consider how many Constitutions were lost during TOS, or the fact that half of the initial production run of Galaxies were destroyed within a decade. It seems possible that most of the Excelsior refits were given dangerous missions, and that is why so few remain today.

What do you think, sirs?

BTW folks, I hate to sound like a nitpicker but, it is improper to call the Ent-B a refit. The ship was built to that spec all at the one time. What were they refitting? The B is an Excelsior-variant.

I can't see any real advantage to the Ent-B design over the normal Excelsior. Starfleet probably realised that the variation is a waste of extra materials and labor. Unfortunately, that doesn't explain why the relatively new Lakota was the variant.

Then they probably just didn't want to pay ILM for the CGI models. They originally didn't for the new FC ships, didn't they?

Anyway, you guys must have read my UP3 write-up, since according to it, the Excelsior II was an explorer variant of the Excelsior. It had more sensors and added impulse engines for redundancy, for when it would be out in deep deep deep space, without capability for rescue from other ships. But, according to my write-up, both the working prototypes, Enterprise-B and Kongo, were both destroyed before the turn of the century, mainly due to system problems. Another reason why Starfleet cut the project after the loss of these two was the fact that such a large explorer type ship wasn't needed, with work on the Ambassador class coming up. Starfleet just needed a large cruiser, which the original Excelsior design could do well. The Lakota was a 'new-era Excelsior II', using the same external arrangement, yet different internal arrangement, for a quick-build medium explorer to compliment to Ambassador.

Do we all agree that Starfleet don't build any more Excelsiors? So, obviously, they would refit the existing ships with the latest kit (where possible/feasible).