I'm not sure which is true.
What I do know is that VSTs opened in Live 4 seem to use up around 50% more CPU than the same VSTs opened in Tracktion, whether you use the Windows or in-software meters to measure it (and this has been confirmed on this and the KVR forum by others doing the same test as I did).
Combined with this - audio seems to drop out at lower CPU overhead in Live than it does in either Tracktion or Adobe Audition.
And what's more, Live doesn't have a freeze/lock function to help with this in any way
During the time I played with the demo I didn't try anything "big" enough to put this to the test or realise that there would be a problem/issue, but subsequently I tried to use Live 4 as a replacement for Tracktion, and my computer simply fell over.
I'm on P4 2.8 Ghz, 512 Mb RAM, and I take the point of some above who say I should upgrade, but 18 months ago when I bought this laptop it was state of the art, and it will be a few months before I next upgrade. Then again, why should I need to when all my other software (also including Reason, Sibelius, and DTP stuff including QuarkXpress, Illustrator, Photoshop) --work just fine? It's only Live giving me problems.
I would like to think that v4.0.5 will help and that I basically didn't just waste my money on Live 4.
Having said that, Robert H's response above seems to me to be saying that Live is great, and that adding new features to lure in new buyers is more important to Ableton than meeting the rather significant needs of those who have already invested in Live.
I may be misreading what he said, in which case I apologise. But if I understood correctly then I have to say I think that is a very bad attitude towards customer support.