...and for music, one can use Google music.
Going over your data limit costs your $10 a month everytime you go over it by 1 byte (the carriers go that low to track data usage). That's just for 1 extra gig.
A 16GB SD card costs $20 at best buy and it's forever.
Accessing data on an SD Card cost exponentially less power than accessing it in the cloud over WiFi, HSPA+ or - God forbid - LTE. This also can exacerbate the embedded battery issues for some people - nevermind the GS3 has a bigger battery than the One X out of the gate and it's still removeable/swappable. You can get 64GB SD Cards (class 6 or 10 Sandisks) for something like $60 these days. Really, the Storage is a real issue. There are many people who will not even consider a phone with that little storage, me being one of them.
I just sold an iTouch and a Windows Phone for something that allowed SD Card Slots because I like to be able to grow my storage as my requirements grow. The One X doesn't have that possibility, therefore it's a terrible value proposition compared to the GS3 and that also makes it less future proof in my eyes. At least with an iPhone I can buy a 32 or 64GB model. There's absolutely no wiggle room with these phones unless you either buy the low end model or want to put up with Sprint's absolutely abyssmal 3G CDMA data speeds.
The Cloud isn't always about storage. It's also about battery and data plan efficiency.
Not everyone wants to sign up for yet another account for something as trivial as storage, especially cloud storage that is borderline useless in low/no reception areas and in Airplane mode on a flight. When you're driving down the interstate and only have EDGE Google Music and DropBox will not do much for you. If you go overseas unless you're Donald Trump and have an unlimited international data plan by virtue of your wealth they won't help much there either. There are too many potential use cases that place the cloud and dropbox squarely on their face - it's disingenuous to even pretend it should be "good" enough for everyone.
Same goes for Google Music. I rather have my music on my SD Card. If you're gonna cache a tone of music offline, you're better off just putting it on the phone to begin with. Google Music is like any other cloud services and suffers the same drawbacks as any of them, especially if your music is encoded at higher bitrates (i.e. 320k MP3s instead of something like 196k WMAs, etc.). I have tracks that are bordering on 20MB in size, and many over 10. I'm not going to stream that kind of data when there are phones available with significantly more storage [possibilities] for basically the same price.
The fact that the GS3 camera is so good seals the deal for me.
TW4 is ugly, so I'm using a Vivid until the GS3 launches. At least that phone has ICS. All I'll have to do is pop my SD card in it before I leave the AT&T store and I'll be set.