> Which one should I get? Which one of those seems like it has the
> highest heat dissipation capability?

C/W is what you should look at

C/W is degrees per watt rise in temperature. So you figure out what
wattage you want to dissipate and find out the temperature rise that
is acceptable. A large or efficient heatsink, for a processor or power
amplifier/supply for example, would be less than 0.5 C/W, especially
if fan-assisted. The 24 C/W heatsink at your link might be OK for a
situation like voltage dropping across a regulator

eg a 12V input to a 7808 that needs to deliver 1A

Voltage drop, 4V. Wattage, 4W (4V * 1A). Temp rise, 96C above
ambient

If you switch your transistor cleanly, particularly a low Rds FET, it
should generate little heat and a probably not need a heatsink. Because
of the voltage drop across a BJT however it probably will. You'll need
to do a wattage calculation to select an appropriate heatsink. Any extra
surface area you can add, eg bolting to a chassis, or efficiency, such as
heat transfer paste or gasket, will help. Matt black is best too, not bare
metal or glossy

Joe
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