I always prefer to go double. The SSD for OS and programs as well as commonly played games. The HDD for the documents.
The best way to go about it. If you do it like this, cheap 128 GB SSD is all you need.
BTW, getting my crucial m4 SSD was the best improvement in computer performance I felt since I replaced my celeron 1.8 with athlon 64 3200+.
Well for some people 128 GB is not enough even for the drive with the OS. This is what kept me from not buying a SSD yet.
128GB is plenty if you are using it "only" for the (a) OS. If you install multiple OS on the SSD then you could potentially fill it up. I have a 240gb installed. Although I intended to use it only for the OS is has slowly acquired other files/programs. I have a sloppy tendency to always download files to the desktop and sometimes when installing new programs I mistakenly install them to the SSD.
One of the unpleasant things about Windows... maybe someone will correct me here (please, please, please!), but I've never found a way to have stuff which'd automatically save to C:/ automatically go to, say, O:/ - you know, stuff which heads to appdata or "My Documents" and other such stuff in "Users." -On the Windows side, that is. Obviously, I tell Core (that always makes me think I'm at some fitness forum...) to use O:/ - but I'm not going to look up every single program to see if there's possibly (unlikely) a way to have saved data moved over to O:/
That's why I have to constantly open WinDirStat for my SSD (if I haven't made it clear by now -- it's a really slick program). There's just so much junk on my copy of Windows, now... but I can't just wipe it anymore without all sorts of issues. All my software's on the O:/ HDD, but all the "vital components" are on the C:/ - which I can't store the blockchain or anything other than the enormous mass of DLLs and Doze files on... so if I wipe it, I lose all those referenced DLLs and similar subcomponent files. You know - and these subcomponents... maybe a piece of software references 10MB worth of data on C:/, so it's ridiculous to have that so "importance-biased."
It's an unpleasant situation. Even if I upgrade my hard drive, I have AT LEAST 200 unique pieces of software throughout my Medusa-like hard drive compound (ha - I don't even think they'd all fit in most PC cases), so I'd be looking at literally days or maybe even weeks to bring them all back to being usable. It's for a similar reason I'm not particularly fond of Steam.... it's difficult to manipulate files -- yeah, I can just redownload the file from them, but on my 3G Sprint connection, it took me a week just to download Empire:Total War a couple weeks ago. I see, you know, some of the Core devs saying stuff like "oh, well the blockchain is only as big as Diablo 3" - but I obviously rely on my primary means of income and expenditure a Hell of a lot more than Diablo 3, so it's kind of important that it's not as cumbersome.
... There are so many things I hate about Windows.... .... maybe time to switch and become one of those assholes who tells everyone else they're the devil if they don't, too.