i've had all four versions, just not the mids. i agree that they end up feeling mostly similar.
the hollows take away from some of that indy clunkiness. forged hollows are a tiny bit lower and lighter, but some of that feeling is negated since the forged baseplates set your wheelbase a little longer. titaniums are the lightest but most expensive for a small reduction in weight.
i do like the hollows on bigger boards with big wheels, especially if you toss risers on, it helps make the pop a little lighter. im also rocking forged titanium 159s on an 8.62" popsicle with 54mm conicals, it makes that board feel a little lighter.
the downside to hollow trucks: that lighter hangar is more responsive to your shifts in weight so they become a little twitchier. forged baseplates makes the board even more wheelbite prone, i didn't like forged hollow 169's they just seemed like wheelbite central.
i also think that the standards roll over crust and grind curbs/pool coping better. its probably because standard hangars have the most momentum from their weight, and not from the physics of vibrations being different through a hollow axle, but who knows? and finally i think *most* pros on indy just ride the standards or hollows, i know chris joslin had a pro model forged hollow though. i never hear about pros on the titaniums but who knows.