Whats faster? a 5400RPM SATA Hard Drive? Or a 7200RPM IDE Hard drive?

Yes, it does!

The SATA drive will read/write data faster than the IDE of the signal that is transferred within the cables from the drive to the computer's system board.

Typically,

- IDE/PATA transfer rates are on the order of 133 MB/s.

- SATA transfer rates are on the order of 150 MB/s (and higher).

Once the data is transferred from the computer system board to the drive, then the RPMs determine how fast that data is written (or read) to (or from) the hard-disk.

So in terms of 'faster' the SATA drive will get information to/from the computer's system board faster, even though it is being written to the disk at a slower speed than the IDE/PATA disk.

EDIT: As of April 2010 the fastest 10,000 RPM SATA mechanical hard disk drives could transfer data at maximum (not average) rates of up to 157 MB/s, which is beyond the capabilities of the older PATA/133 specification and also exceeds a SATA 1.5 Gbit/s link.

(1.5 Giga-bits/sec = 150 MB/sec)

Most new computers use SATA interface rather than the older IDE/ATA. You have to use the type supported by your motherboard.

Also most laptops use 5400 rpm rather than 7200 because of battery savings.

No, the slower spinning would cause the computer to run slower.