3.5" external HDD vs 2.5" external HDD

Hi, I am considering purchasing an external hdd, but I would just like to know whether it would be better to buy a 3.5" or a 2.5". Are there really any major differences between the two?

"Are there really any major differences between the two?"...
In a word, No

There are, in fact, differences.

2.5' usually have a lower power consumption, since they do not have an external power supply. You just plug them into a USB slot and go. The 3.5' do have external power supplies, and usually consume more power. That being said, this varies per model, of course.

Furthermore, since the 2.5' external hdd's are usually based on laptop models (that's why they require less power) they are usually also slower, rotation speed wise. Then there's the obvious difference of size.

Finally, the price is usually different. One pays more for a 2.5' hdd with the same storage space as a similar 3.5' hdd. The real question is therefore: what are you looking for in a harddrive, and how much are you willing to pay for it?

Thanks guys, I appreciate your input .