Sprint started running weird commercials with cartoon robots yammering about “First is 4G” a long time ago. Now T-Mobile keeps crowing about 4G in their TV ads with that skinny woman in the loud dresses. People are complaining that iPad 2 doesn’t have 4G. I keep writing and tweeting about how awesome my Verizon 4G modem (which I’m using as I post this) is.

What is 4G, anyway, and why should you care? Or should you at all?

The best way to explain what 4G is isn’t to throw a ton of acronyms and specs at you. Trust me, I tried that approach and my colleagues told me to Select All, Delete, and try again lest I scare all of our readers away. The best way to explain what 4G is is by comparing it to 3G when it comes to real-world usage and where in the real world you can and can’t get you some Fourth Gee.

4G is… 3G is…

4G is streaming video. 3G is streaming video that’s a little slower to load and a little lower quality.

4G is video calls. 3G is sending video messages (or hacking your phone to make low-quality video calls).

4G is browsing the Web. 3G is browsing the Web, slower.

4G is fast enough that working on your laptop will feel pretty natural as compared to using your local coffeehouse’s WiFi. 3G is getting work done on your laptop with occasional – or semi-frequent – pauses to stretch, pee, and refill your coffee mug while you wait for things to load.

4G is downloading songs on the go. 3G is downloading slightly lower quality versions of songs on the go.

4G drains your battery faster than not-4G. 3G drains your battery faster than not-3G.

4G is not available in very many places, and those places are mainly in the United States. 3G is not available everywhere but is available in many places in the U.S.

4G will work on your 4G-enabled device. 3G will also most likely work on your 4G-enabled device when you’re out of 4G range. But not always. Check with your friendly salesperson before you buy.

4G is currently available on a small handful of phones and modems in the U.S. – iPhone is not one of them. 3G is pretty hard to avoid at this point if you’re shopping at a major US carrier’s store.

Pro Tip: If your cellular signal is lousy, your data connection is bad, and your battery is dying rapidly, turn off your 4G and your 3G. This is what all of the savvy iPhone users do at CES when the AT&T network in Las Vegas crumbles amidst the iPhones inside of the casinos and convention center.

That’s Oversimplifying it, though. So let’s dive deeper.

4G varies from carrier to carrier, town to town, and building to building.

4G performance isn’t just about raw download speeds. It’s also about latency (how long it takes for you hitting a button to register on the network) and upload speeds. Want to play multiplayer games on the go? Low latency is your friend. Want to send PowerPoint presentations to the office from your smartphone? Fast upload speeds are key.

Image via Wirelessweek.com

4G on Verizon’s LTE network is faster than 4G on T-Mobile’s HSPA+ is faster than 4G on Sprint’s WiMax is faster than 4G on AT&T’s HSPA+ Verizon’s 4G is legitimately as fast as my Comcast Cable modem, though I do have a semi-cheapo plan.*

*(In my personal experience in California and Las Vegas, anyway)

4G on LTE and HSPA+ works better than 4G on WiMax when I’m indoors and not hanging halfway out of an open window. It’s more complicated than that, but things like “line of sight” and “building penetration” effect networks of all sorts, particularly ones that are newly being rolled out to consumers.

4G on LTE offers the best upload speeds. By a longshot.**

**(Again, in my personal experience in California and Las Vegas, anyway)

4G is defined differently now than it was just a few months ago, thanks to the unrelenting marketers who work for the major U.S. cellular networks. In the “olden days,” none of what we now call 4G came close to qualifying for actual 4G status. Marketers changed that so they could sell you stuff. “Real” 4G is wayyyyy faster than the cut-rate stuff we’re now being sold.

Enjoy the Speed, Don’t Believe the Hype

In sum, 4G is better than 3G. Is it better enough to warrant buying a new 4G phone/data modem and paying extra for 4G service? That, as everything in this business, depends on where you’ll be using it and what you want it to do. If you really want to make video calls, watch streaming video, browse multimedia-rich Web content, download tons of video and music, or do on-the-go laptop work at in-the-office speeds, it’s worth looking into the cost and availability of 4G in your neck of the woods. Take into account all of the variables, from coverage maps and data caps (unlimited data is dying, sadly) to what phones and modems are currently available and whether or not they’ll work for what you need them to do.

Example: Like I said, this Verizon LTE modem is just as fast as my home cable modem where I use it. But the Verizon service plan has a data cap. I work online literally all day, all week, and I upload a lot of video. So ditching my cable modem for a 4G-only lifestyle would very quickly result in overage charges big enough to put me in the poorhouse. LTE on the go when I really need it? Great option. LTE to replace my home service? Not just yet.

4G is not readily available just yet, even in the marketing-happy US. Even in areas where 4G is available, it doesn’t work in as many buildings, airports, cafes, nooks, and crannies as 3G does. 4G on Sprint is very different from 4G on Verizon, from T-Mobile, and from AT&T and MetroPCS. The number of 4G-capable devices currently on the market is pretty small; very small in comparison to the shelves full of 3G phones that were all super whiz bang shiny and new just a few months ago.

That said, even in today’s “not really 4G” forms, 4G is somewhere between faster than 3G and really freakin’ fast, depending on the who/what/where of your service. Me, I don’t think it’s worth opting for a 4G device just for the sake of 4G. But I do think it’s worth thinking about, or even paying extra for, if you know what it can and can’t do for you in the near-term.

4G Buying Advice

Mobile devices generally come hitched to two-year contracts in the U.S. You already know if it’s worth paying the extra fees for an early upgrade to a 4G device and plan; if you’re not sure about it, the answer is No, don’t do it yet. If you’re in the market for a new device, however, it’s a bit trickier. Signing on to a 3G device for two years might come back to haunt you if you’re on the 4G fence today – ask your salesperson about options and fees associated with upgrading before your contract is up. Then again, if your heart is set on an iPhone, G2, Pre 3, or other non-4G phone, are you really going to be happy with something a little bit faster that you actually hate looking at every day? No, probably not. Enjoy the speed but don’t believe the hype: 4G is coming for all of us, but only now a reality for a small few.