I am running out of disk space in my desktop computer and I am thinking of adding a new hard drive to it. However, I am having a second thought whether to buy a new hard drive or just buy USB drive. Which would be better off? I heard that USBs can hold more files and are faster in transferring files, but hard drives outperforms them in terms of I/O performance. 
Whether it's the hard drive or the USB drive that can hold more files is dependent on how much space they have, the interface doesn't really have anything to do with it. File transfer speeds depends on the interface being used. If you're going to use USB 1.0, you'll have a maximum of 12 Mbits per second. If you'll use the USB 2.0 interface, you'll have 480 Mbpit per second as the maximum. If it's going to be USB 3.0, that'll be 5 Gbits per second.
If you have an IDE interface for your hard drive, you'll have a maximum of 133 MBytes per second if you have the latest version. If you SATA, SATA 1.0 has 1.5 Gbits per second speed, SATA 2.0 has 3Gbits per second and SATA 3.0 has 6 GBits per second.
Hi Loucarl,
First you need to know about the technology advancement of both hard disk and USB. The capacity is not that matter but the File Allocation Table does matter. If a USB is comprised of digitally drive to save data digitally where as hard disk provides a source of magnetically charged disks to store the data. As far as the speed is concerned the hard disk drive has a better rotation speed than a USB 2.0 storage speed.
Its speed also depends on the USB 2.0 Port that was used before 2008 since the latest USB 3.0 provides the highest speed usb available on Philips and NEC USBs which can transfer up to 480 Mbit/s, a forty fold increase over USB 1.1 specifications. So you see according to the technological achievements the USB’s are compared with hard disks not with their capacities to store the data.
Hope this might help you
Hello Loucarl
Well i would suggest you to go for a hard drive as it would be more spacious and reliable. A pendrive is a portable device which can store data but a huge amount of data is not safe for a pen drive. It can malfunction anytime. Moreover if there is a huge amount of data then it becomes really slow to transfer data to system. A pen drive beyond 8 GB is a waste. It is because data processing becomes too slow and keeps on transferring data for hours.
So it is better to go for a Hard Disk than to go for a pendrive. A Hard Disk outperforms a pendrive in every manner. It can store huge amount of data,it is faster than a pen drive,data remains safe in a hard disk as it is stored internally. Moreover if you want a portable device which can connect via USB then I would suggest you to buy a portable external hard drive which is very common nowadays and you can carry it anywhere around.
Hope this helps.
Thank you
Gaurav3282
