You can't really rush through the game with Richter or Maria. Well you can, but you'll never make 200% complete on the castles. I want to see you beat Galamoth with Richter. You can only do the item crash Holy Rain so many times since you max out of hearts way lower than Alucard who can actually level up. On top of that only three hits from Galamoth can kill Richter since he never levels up and Galamoth has way over 9999HP. The guy is hard to beat with Alucard and near impossible with Richter. At least with Maria you can use her spells which grant her a few seconds of invincibility while the attack is going on. Though even though the screen stops when she casts them, Galamoth can still move as the stop ahas the same effect as using the watch, which Galamoth can also move through, albeit slowly.
As for the slowdowns, the PSX had the same slowdown issue when there were a load of guys onscreen. The whole problem with the PSX->SAT ports was always that they just never did anything to optimize it for the new machine. That's why you see these same issues pop up again and again in Drac X, Rockman X3, Rockman X4, Rockman 8, etc etc etc. I have to agree, these ports seems like 2 week projects to squeeze more money out of the same game.
As for the new wings of the castle, they were obviously designed by someone other than whomever made most of the rest of th egame graphics. The enemies and layouts stick out like a sore thumb and have a very fakey/afterthought feel to them.
I liked the Saturn game well enough but yeah, it's a real shame they just didn't do more with it. At the very least they could have actually given Richter and Maria some form of story. A leveling system or a tech system would have been nice too. You could have had a new pattern of advancement through the castle if U,D,U+Attack was disabled till you learn it later.
As for beating Symponhy of the Night/Gekka no Yasoukyoku. I've clocked it with Alucard and if you know where to go, it's a six hour game to get through both castles. It's really not that much longer than Simon's Quest which in my opinion, was a far more challanging game. Jumps were far less forgiving in those das and enemys rebounded ou so hard it could send you off into the water. The original Akumajou Dracula was considerably easy. It only took a few hours to beat and didn't offer THAT much of a challange. But 3 was quite hard. The multiple paths also added a lot to the game for replay value. the original Dracula X on PC-Engine was an impressive game in that respect as well. I think playing as Maria and being able to throw birds was incredibly cool. She added a fresh control aspect to the game that Grant and Syphon just didn't manage in 3. The game also had loads of secrets, keys to find, people to free, hidden exits, etc. Finding everything in Drac X was way harder than the SotN sequel. And the fight with the Grim Reaper on the ship was even more annoying than Dracula.
Games today are missing the tight, unforgiving controls and timing they used to have. They can make them as long as they want with as pretty of graphics as they want, but it's just not there. There's nothing like jumping in a NES game and realizing it's a fixed distance and no matter how much you mash at the control pad, you're falling straight into that enemy who is going to knock you back into the pit. And then it hits you "I am soooooo dead". --GAME OVER--