Since most users have abandoned desktops for laptops these days, I think the 2.5" drives make a better choice than 3.5" drives (that require power adapters).
BUT... I use 2.5" drives with my mini (desktop) because I can get dual drive enclosures that DON'T have to have a cooling fan. I like my nice, quiet Mac mini.
And since they're fan-less, I can keep an immediate mirrored RAID backup of all of my most important files (the thousands of pictures of my new baby girl and my movies), as well as a Time Machine backup, too. Yeah, I'm a bit obsessive about backup.
I do, however, have a couple of 3.5" single drive enclosures - one is my Time Machine drive, the other is a documents "archive." (I'm a bit of a digital pack-rat, lol) Not sure what I'll do when these need replaced, whether dead or full - I guess it all depends on prices and sizes at that time. For now, I'm good on both fronts.
That all being said... I'm a fan of Western Digital.
Haven't had a single failure of a
personal WD drive in 20 years of computer use and repair/upgrade. (And being a tech-geek I've had PLENTY of computers and hard drives, both internal and external.)