OK, I have one of each of:-

1Tb 5400 rpm with 8Gb SSD hybrid
1Tb 7200 rpm

Which shall I use (be generally faster) in a new Win7 install? I can only put one HDD in the laptop…

Well windows 7 32 needs 16gb 64 needs 20gb of space so I’d be going with the faster spinning drive
http://windows.microsoft.com/en-au/windows7/products/system-requirements

I’d expect the hybrid drive will be quicker, and use nominally less battery.

If you can do with less storage consider a 256 of 512Gb SSD and get an external HDD for the rest. A good SSD (Samsung 840 or Crucial M500) will be significantly faster than the spinning discs. Once you’ve used a machine with an SSD you’ll wonder why you didn’t do the switch years ago!

I don’t have an SSD unfortunately, I have the above two drives! This is not a computer to spend money on 🙂

Think I may bung the hybrid one in and use the other one for back ups in a USB caddy.

Depends exactly how you are going to be using the pc, but in most situations the hybrid will be faster.

Hybrid as it puts the most used files on the ssd portion automatically, will be very close to ssd speeds.