I don't know where everyone gets the idea that stainless is so heavy. Out of curiosity, I used the online calculator, and a 2" diameter, 2' long, 21 lb bar of stainless is only 1/4 to 1/2 lb heavier than chromoly. (Depends on the alloy) I know somebody is going to say that a stainless axle would need to be bigger diameter than a chromoly axle to be strong enough. I call BS. An aftermarket size, stainless axle is still going to be stronger than any aluminum drag axle.
As for the original question, stainless and Ti look very similar. Only way I know to tell the difference is to try to run a file across it or weigh it.