A 2nd drive is great. I can’t think of a case where it would cause a problem.

One thing a 2nd drive is often used for is backups. When it fills up, you can pull it out and put it on a shelf, then put in another drive and fill it up. This is pretty much the only case where a HDD is better because if you leave an SSD on a shelf for years, it can lose data.

I like to put my data on a 2nd drive. I tell myself it’s safer because the data drive will last longer since the operating system drive does lots of small writes all the time. But this is marginal. I use another SSD for this.

It sounds like your friend has a specific need for an SSD right now and you don’t. The HDD isn’t an even trade but it’s what he has. You’d be doing him a favor and it’s up to you if you want to.

Often isn’t an issue. It’s only if you take it out of the computer and put it on a shelf. Years later, the HDD should still have the data but an SSD may not.

What are you planning on putting on the second drive in your laptop? Game files? The SSD is better. Backups? The HDD is better (HDDs can be left unpowered for long periods without risking data loss and SSDs can’t) The SSD is probably worth a bit more than the HDD but neither is worth a lot anyway. If he’s going to use the SSD as a boot drive vs a HDD, that would be a big difference for him. If you have game files or other large amounts of small files, the HDD would be noticeably slower for you but not as bad as using it as a boot drive.