Should I be buying a 2.5" HDD or a 3.5" HDD?

[Vozella]

What's the difference?

[Tedol]

size 

[meatdeluxe]

2.5 for laptops
3.5 for desktops

SSD's come in 2.5 and will work in a desktop just fine

[Guest]

Size, and typically Rotational latency/rotational speed. 

 

Majority of 2.5" HDDs have a rotational speed of 5400rpm, whereas most 3.5" HDDs have a rotational speed of 7200rpm. 

[SPG]

which ever one has the higher rpm, if they both have the same rpm, there is no difference aside from size (and maybe capacity) 

[Lethal Seraph]

Size. 2.5" usually fits laptops, and all SSDs. 3.5" fits all desktops.

 

But you can also buy a mount converted for the 3.5 to fit 2x2.5" HDDs.

[TheMcSame]

3.5" hard drives are for desktops and should be used unless you physically can't mount it anywhere. 3.5" drives are significantly cheaper.

 

2.5" hard drives would be for laptops because laptops don't have 3.5" mounts.

[TheKDub]

You can buy either for a desktop, or if its for a laptop get a 2.5" drive.

 

Typically 3.5" HDDs are cheaper than 2.5" HDDs, though SSDs don't come in 3.5" variants.

[Deli]

Even for both 2.5" and 3.5" with the same rpm, the 3.5" will be faster and more responsive. I have a WD 2.5" Black 750GB and a WD 3.5" Blue 1TB connect to the same PC. They are both 7,200rpm. The 2.5" Black has about read speed of 100-110MB/s. While the 3,5" Blue has 160-170MB/s. You feel a very noticeable difference when using them.