hash - SHA-256 or MD5 for file integrity

Question

I know that SHA-256 is favored over MD5 for security, etc., but, if I am to use a method to only check file integrity (that is, nothing to do with password encryption, etc.), is there any advantage of using SHA-256?

Since MD5 is 128-bit and SHA-256 is 256-bit (therefore twice as big)...

1. Would it take up to twice as long to encrypt?

2. Where time is not of essence, like in a backup program, and file integrity is all that is needed, would anyone argue against MD5 for a different algorithm, or even suggest a different technique?

3. Does using MD5 produce a checksum?

Answer 1

Both SHA256 and MDA5 are hashing algorithms. They take your input data, in this case your file, and output a 256/128-bit number. This number is a checksum. There is no encryption taking place because an infinite number of inputs can result in the same hash value, although in reality collisions are rare.

SHA256 takes somewhat more time to calculate than MD5, according to this answer.

Offhand, I'd say that MD5 would be probably be suitable for what you need.