The first Sol is not much different from the orginial series Enterprise except that the Science Department is much smaller, the shuttles have been replaced by ground attack craft, Starfleet Marines run the shuttle bay and the trainning of the crew is not for exploration or diplomacy but combat.

The Sol A saw some battles, but this was a fairly peaceful time and a modified heavy crusier was all that was needed. It's destruction signaled that it was time for a more powerful battleship.