Which of these two games has the deeper storyline for those of you who have played both?

Xenogears, by far. It explores just about every single theme and concept imaginable in the greatest of details, contains an absurd amount of symbolism and is generally of far greater scope. Planescape: Torment is pretty weak by comparison.

hum ... never played xenogears

but I doubt any JRPG can match Planetscape torment story and character developpement

Neverthless, I have not played Xenogears myself ....

weak how?

JRPGs tell the best stories you can find in any medium, and Xenogears specifically is the very best the genre (and storytelling of any medium) has to offer.

It explores the philosophical ideas of Friedrich Nietzsche, Sigmund Freud, Carl Jung and Jacques Lacan, it delves into the nature of God, The Universe and existence, the nature of human memory, the struggle between man and machine, the horrors of war, ethics, politics, economics... the list goes on, and it does so with such detail and scope.

But beyond that it's quite simply just far more complex (complicated subject matter, complicated narrative, so much shrouded in mystery and ambiguity, with plot twists that make you question everything you had been lead to believe about the game's story) and compelling (helped considerably by its phenomenal music, as well as the fact that it touches on just about every single emotion of the player) than Planescape: Torment, and the same's also the case with Chrono Trigger, Chrono Cross, Radical Dreamers, and the Xenosaga series.

Any JRPG except Xenogears & the Xenosaga series :P

Can you say anything specific about where Planescape:Torment's story was weak?

I'm going with PS:T myself. Xenogears had a lot of potential, but it's a heavily-flawed game in many ways that PS:T simply is not.

This is a pretty tough choice, since both games are at the top in terms of story-telling and development.

I'll go with Planescape Torment though, the Nameless One story and how it came to be is simply too magnificent to disregard.

I was reffering to something it lacked, not something that it possessed, when I reffered to it as weak [in comparison to Xenogears], so a specific example isn't something that can really be cited. The simple fact is that it does not cover anywhere near the number of themes that Xenogears does, and with nowhere near the detail.

In what ways was Xenogears flawed?