SoU's Ch.2 was very rushed and this was even acknowledged tongue-in-cheek in HotU's opening, Deekin asks if you read his book about your adventures and you can reply that it dropped off towards the end. SoU wasn't actually developed in-house by BioWare, but contracted out to Paul Neurath's Floodgate, and it definitely looks like they set out to iterate on the OC but maybe ran out of time towards the end.
But I loved it, precisely because of its more compact nature, in part. The OC just spread its content over too many gameplay hours, SoU felt more focused and better paced. I also liked it gimmicky dungeons, there was more bespoke scripting going on over there, and I adored the setting for its second chapter, a shame it was so short, I could spend twenty hours in something like that withough getting bored. A big feather in the campaign's cap was introducing persistent henchmen with inventory access - where the OC had a very rudimentary set of blokes they just copied from module to module with updated stats, Xanos and/or Dorna actually follow you through the adventure and you can deck them out how you like. They didn't have a lot of personal content, sure, but the OC's "level up, get exposition 1/2/3/4, find thingamajig" was grating and SoU's companions somehow felt like more of a genuine presence. Another thing that was improved was level design and loot distribution - I recall the OC dragging out room after room with the same encounters just to let you at a whole bunch of locked, trapped chests that only spawn RNG loot, but SoU felt like consolidated things into fewer containers with better stuff.
Anyway, official NWN content for me is TotM > SoU > DoD > HotU > OC. DoD's great, it should outrank SoU from an objective standpoint, but for some reason I remember the latter more fondly, probably nostalgia. As for HotU, the first chapter's great and so's the third, but for the middle one... I hate the Underdark. Caves, bleh, booo-riiing.
