I want to buy some storage but I don't know which to choose between this Seagate and some external usb 3.0 hdd which I would use connected to a 2.0 usb port. Is the speed difference that high? Thanks!
The Seagate internal is a SATA III drive (6Gb/sec) so if your motherboard also supports SATA III the drive will be way faster than an external one on USB 2.0
Also less clutter on your desk if you get an internal one, and generally more reliable owing to the fact that external ones employ a bridge-chip inside the enclosure to convert SATA to USB, and this can sometimes fail.
Having said that, I've got three WD externals and they've been rock solid for 10 years. I need externals for off-site backups & for easy transfer of docs & pics to other devices.
2.5 and 3.5 drives should perform exactly the same if they are 7200 rpm drives.
Many 2.5" laptop drives are 5400 rpm and slower.
An external drive is likely to be more constrained by the usb connection speed.
A HDD is a good device to store video files which tend to be large and are accessed sequentially.
For windows, I think a 120gb ssd is way too small.
Many things default to the C drive.
When a ssd becomes 90% full, it starts to lose performance and endurance.
I would include a C drive upgrade in your plans.
What is your motherboard? Can it support a m.2 device?
I have an ADATA SU650 SSD connected to a sata 2 motherboard. I'm satisfied with the overall speed of the system, but I need a HDD as a secondary drive. I don't want to buy another SSD because the cost is too high for the capacity I need.