You're missing... waiting for the stones to soak, making a huge mess, faster dishing/needing more flattening... But you're also missing a more traditional experience, and one which imho not only subjectively feels better and offers more subjective control but also works better in a great many use cases. The soakers have an level of feedback which means a level of control of what's happening down there that's hard to match on a splash and go. They also tend to cut very fast, which goes along with dishing faster. I also find there to be a lot of versatility, which you can also get on splash and go by playing around with pressure and slurry, but it's on another level with a soaker. You can play around with subtle adjustments to get a variety of end results in terms of finish and whatnot. I find it more pleasurable and perhaps easier to get more controlled and defined results with a good soaker. I'm just wary about using them on something like hap40 at 65+ rc, cuz I feel like the stone is gonna win the fight in the end but take a beating in the process. I'm probably missing and forgetting stuff as usual but I think that about sums it up.
The cool thing about something like the Naniwa Chosera/professional stones is they are like hybrids. Though they are magnesia bonded so they can not be permasoaked or anything like that, they do have the "vibe" of a soaking stone, and are quite thirsty. They take a lot of water and have a feel to them that for a supposed splash and go gets pretty close. It's like a hybrid is what I'd call it. As opposed to something like a shapton pro which even at the lower grits seems to absorb little to no water and is ready to go with just a splash. Te surface is too hard and maybe glassy for some people and some uses though. Shapton glass stones are also ready to go with just a splash, unlike choseras imo, but they also seem to "paradoxically" have a very nice feeling to them, even at higher grits. I think it comes down a very control way in which they break down and release particles. It seems to be happening in a very controlled way which makes a harder stone feel.. different. IDK if that made any sense.