I wouldn't necessarily say the combo is better than a single SSD. The SSD with the operating system on it makes your system much more responsive. Windows boots faster, apps load faster, things like virus scans and other tasks run quicker. The reason an HDD is added is to give additional storage for data since the price per GB is lower. If you need a lot of storage and can't afford a bigger SSD, this is a cost effective solution. If you don't need a lot of storage, then a single SSD is perfectly fine. I have a laptop that only uses a single 120 GB SSD without issue. You just have to be mindful of what you install and periodically clean up the drive to remove unused programs, temp files, etc. 240 GB SSD's are coming very close in price to a single 1 TB HDD which isn't an unreasonable size unless you have a big game library or a bunch of movies or music.