Being the same weight as you, and knowing that those 25mm tubies are true 25mm's, I would raise the pressure a bit. Vittorias are nown to remain very supple, even at higer pressures. I run my Michelin Comp 25's (27,5mm real) at 90psi. If i go lower, the bike becomes slighish, soft and somewhat slower. On very good roads, I would run them at 100psi. But i'm with you that 100gr penalty on the seat is really felt. When I put 28mm conti 4000s (275gr) on my Canyon, coming from 25mm 4000s (around 220gr), that was a massive differerence in sense of responsiveness and accelaration. Not slower on the flat's and when on speed, but in every other situation, the bike felt slower and a lot more heavy!! But what a pease of mind, even on gravel roads and (not too bad) single tracks.
So, to the OP, at your weight, I would keep running 23's on wide rims with just enough pressure in the tyres to prevent a too 'soft' feel.
I've tried a range of pressures on the 25s and i've settled on 100psi for the rear and 95 for the front. And yeah, the tires don't feel as floppy as they do at around 80-85, but at a full 7 bar they really aren't any more comfy than the 23's either, and you are still lugging the weight penalty and the increased radius around (I believe, though i'm not entirely certain, that a fatter tire with a bigger radius is slower to turn in because the contact point has to move sideways more than on a narrower tire when you lean the bike. Again, I could be wrong)
Your perceptions about the tires match mine almost exactly. As you said, once you're up to speed you can't really feel any difference besides the comfort (if you're running lower pressures...), but the moment you have to accelerate, throw the bike quickly into a turn, climb out of the saddle etc, they just don't feel quite as sharp and nimble a tool as the narrower tires.
Also something I didn't mention before, I think the feeling at the edge of grip is very different between the two sizes. Whilst the 23's start getting skittish and sort of jumping around when you're pushing them too far in a turn, the feeling I get with the 25s is sorta like they were "folding over" themselves. I find this to be the case at all reasonable pressures and alarmingly so at anything below 85psi in the front tire. I like the "skip and jump" kind of warning a lot better than the "folding over" kind.
I'm lucky in that I live in Mallorca and most of the roads here are great and I don't really need the extra comfort, so It's gonna be back to 23mm at 110psi front and rear for me real soon.