The S4 is actually smaller than the S3, despite the larger screen size. It's the same height, but it's a hair narrower, a couple hairs thinner, and a few feathers lighter. Pretty impressive. It's an amazing phone, to be sure, but I don't know if it'd worth upgrading from the S3 just yet. The S3 is still extremely capable and will handle anything you can currently throw at it app-wise. If you like your S3, I'd honestly wait until the S5 comes out. If I owned an S3, I personally couldn't justify the upgrade to the S4. Rumor is it'll have at least partial metal construction, so it'll be a more premium feeling device than Samsung's typical boring plastic.
If you want to make a big change, the Note 3 is where it's at. This thing is a monster. Both in size and in power; most people's laptops are humbled by the Note 3's specs. The S-Pen stylus adds functionality that most people don't use, but from what I gather about your profession and how you use phones/tablets, you might get great use with the S-Pen. And since the screen is so large, you might not have to lug around a laptop or tablet.
The Moto X is an interesting device. Middle-of-the-road specs, but with unique features that make it very fast and great to use. The screen won't be an improvement over your S3. It has slightly smaller dimensions, but it's thicker, and just as heavy. Despite its features, there's a few things that would prevent me from getting one myself, or recommending one to someone. First, it's thick. I like thin. Second, the battery is only of average size, and it's not replaceable. If you use your phone a lot, you're going to need to charge it a lot. My phone is a Droid Razr Maxx, and its huge battery is the reason I bought it. Alternatively, you can always buy a second battery for your S3 or S4 or S5 or Note 3. Not so with the Moto X. Third, the Moto X doesn't offer a microSD slot. For me, this is a deal-killer. For you...I can't say. Depends on how many apps you use, and if you fill up space with music/videos/etc.
Regarding the iPhone 5s; I'm biased against Apple for various reasons, so it's hard for me to recommend them. But they are nice phones, and the app selection is second to none. If you already have the 4s, and you really, really like it, then by all means, get a 5s, but all you're really getting is a slightly bigger screen (which is still small compared to your S3). If you're already required to lug around an iPhone 4s, you might as well get an Android so you've got all your bases covered. If I had to be stuck with an iPhone, the 4s would be my choice, since it is smaller. One thing that Android phones are lacking is a powerful, yet small device. Any small Android device is a cheap, budget, piece of crap.
You can pretty much ignore any other phones offered by US Cellular, except perhaps for the Kyocera Hydro XTRM. It's a tough phone, and waterproof. Its specs aren't anything to brag about, but it's tough, and it's waterproof.
To sum up...
Were I in your position, I would get the Note 3, because that's what I'm planning to do myself in 4-5 months. But it's a massive phone, and certainly not for everyone. The reason I want one is because my "phone" is less a phone and more a pocket computer. I use a ton of data, a fair amount of texts, and practically no minutes with my phone. If the Note 3 isn't your cup of tea, then I'd just wait until the S5 or something else just as juicy comes along. The S4, while nice, isn't enough of an upgrade to justify the cost and contract extension. Apart from the fingerprint scanner and a slightly bigger screen, the iPhone 5s won't give you much more of an experience than the 4s you already have.
My Son had a Samsung Galaxy S4 that he bought last Spring.He got the insurance too from a company called Esecuritel. Anyhow last September I used it and it slid off my lap on the patio and scratched the screen slightly,no big deal just cosmetic. About two weeks ago it would not take a charge so we took it to the authorized repair shop to have them tell us the problem .Turns out there was a bad connection inside the internal charging port that they said could not be fixed. My Son called the insurance and they asked if there was any dings ,scratches,ect. on the phone.He told them about the little scratch and they said since he didn't report it immediately they WOULDN'T honor his insurance PERIOD,end of story!
