i used to have a selle italia ti flight or whatever it was. probably one of my favourite saddles of all time. unfortunately, it's also the only seat on which i've ever broken a rail. i'm not saying that ti breaks easier, just saying the only seat rail i ever busted was made of titanium.

i don't think the rails have anything to do with the comfort of the seat. the actual shell, padding and covering will detemine that.

aside from that, you shouldn't really notice the weight difference unless you've got an ultra light ride and you're super weight conscious. it's like hubs: some people claim they can tell the difference between high end hubs and low end hubs by riding the bike. and some people claim they can tell the difference between a few hundred grams of weight.

if you want a ti railed saddle and you can afford it, go for it. it will make you feel good.