There's quite a few campaign improvements. Myself, I much prefer the Jutland campaign - I find enemy actions to be much more varied and dynamic for one, I think the scripting for enemy operations has become much more varied. The British and German sides are about as different as the Russian and Japanese side, and the AI for both seems to be quite a bit more active - constantly laying mines, sending out bombardment missions, and unless you give it a beating, making a variety of sorties. If you play with Room 40 on, the British get reports on when German ships leave, and, AFAIK if the British side is AI then they generally get additional intelligence on where your fleet is going, which makes them a lot more effective at making intercepts.
Area patrol logic is much improved, so now you can set a patrol radius for your dispersed task forces, which now means they don't wander all over the map and you don't spend most of the campaign in 1 vs 1 small ship engagements and chases - these lone patrols just don't meet much anymore. You also have subs and zeppelins that mostly play a campaign-map role in helping deliver intelligence, and if the subs are lucky - pop a torpedo into an enemy warship (unfortunately right now it seems like the subs are a bit of an overpowering menace to light patrols - hopefully this'll get fixed in a patch soon, since they're unusually good at sinking destroyers and TBs at the moment).
My favorite thing about the campaign in Jutland, though, is a tactical game rather than strategic map change - you have "advanced critical hit" options that seriously affect British tactical effectiveness, and can make the campaign battles seriously difficult for one or the other side depending on how they're set. When set historically, they give the British a serious handicap, especially if you go out looking for a decisive engagement. That's actually a very good thing for experienced players, I find, since these actually make up for some of the tactical AI's foibles. That said, in recent patches the tactical AI in Jutland has also improved a lot and is now definitely better than the RJW game.