Cadillac CTS & STS differences/similarities

[Chevy454]

A freind of ours is looking for a Cadillac CTS or STS, but had some questions, which I couldn't answer. One had to do with the amount of "room" inside, in a CTS versus an STS...my understanding was that they're both made on the Sigma(?) platform, so I kind of figured they ought to be pretty close to the same as far as interior room...any other striking differences, other than price?

[georgejetson]

STS is somewhat bigger, both longer and wider -- it's particularly noticeable in the back seat -- and plusher, with more luxury doodads available. V8 STSs have the N*, which was never used in the CTS.