Better an X60 with XP or X61 with Vista and Turbo Memory ?

[brosen]

My current system is:

X60: 2Ghz CPU + 4G RAM (only 3GB) + 250GB HD + Windows XP

The system runs very good, nonetheless I was thinking to buy an X61 mainly because I will be able to use the full 4GB RAM (with Vista x64) and I could have a little bit faster CPU 2.2Ghz, faster Buz 800Mhz and the 1GB Intel Turbo Memory for the HD.

X61: 2.2Ghz CPU + 4G RAM + 250GB HD + Windows Vista x64

But then I realized that, it is true I will have a faster Hardware, but Windows Vista x64 is MUCH HEAVIER than Windows XP, so maybe bottom line the whole system with Vista will be slower than my current system with XP, what do you think ?, I have not tried my current system with Vista yet.[/b]