Note: This post originally appeared on AppAdvice.com on Friday October 7. We believe it’s worth bringing it out again for the iPhone 4S launch day. This is only a recommandation, and doesn’t apply to everyone obviously. Enjoy!

We know many of you, enthusiasts and others, are pre-ordering today or will be standing in line for the new iPhone 4S comes next Friday. Yet, while you might have already settled on the fact that you want the newest and greatest iPhone 4S (congrats!), it might get complicated to pick the right model. Indeed, in the US, the iPhone 4S comes, just like the iPad 2, in 18 different variations across carriers.

To help you decide which one should be yours, we’ve considered all the aspects and made a simple, three-stage explanation that will bring you to the right decision, one you won’t regret.

Black or White?

As far as color goes, it’s of course very subjective and a matter of style. However, it’s interesting to bring back the same argument we made against the white iPad 2 as it’s still valid:

A white bezel will you give the impression that the screen is dimmer, and has less contrast. The content won’t stand out as much. There is a reason why TVs come generally in Black, and letterbox content with black frames. White will make your movies and games look worse. Then, a white Frame will also reflect more light when you’re outside, it will be more visibly dirty and worse of all, white Apple products have a long history of problems, from cracking, delays to light leaks and so on.

The same applies to the iPhone, and even more so as you’ll have it on you all the time, and it’s more likely to get dirty or scratched.  Unless you really want your device to look different from everyone else’s (the black is the most popular color), the black iPhone 4S is a much better, safer choice.

16, 32 or 64 GB?

How much space you need depends on your usage and your music library. The iPhone 4S comes with a choice of either 16, 32 or 64GB of memory. Needs are however hard to assess, so we did it for you.

Apps = 6GB

We proceeded to make a selection of the 100 most common apps, including a full US GPS navigation app (Navigon), a DivX player (CineXplayer) with 5 episodes of 45 minutes TV shows inside (Fringe),  a few games (mostly small one, but including a few larger too) as well as a bunch of emails and pdf documents. It took just under 6GB to fit. This is all you’ll ever need in most cases.

Music & Podcasts = 10GB

For music, a simple collection of 700 songs will take approximately 4.5 GB. If you like podcasts, and have signed up to about 10 different ones, with 5 episodes of each, it will take you a further 5GB. All together, count about 10GB. Of course, this is likely to change a lot depending on your music collection. If you stream most of your music using Spotify or Pandora, you’ll need much less.

Photos & Videos = 5GB

The new iPhone 4S packs an amazing camera that can make 8MP shots, and record 1080p HD video. If you’re hoping to carry around about 200 pics you made, plus another 200 of your favorites you synched from your computer, and about 40 smaller clips, you’ll need a further 5GB.

Settings + Books = Negligible

Unless you’re planning to carry a couple hundred pdfs, or a library of a hundred books or more on your iPhone (unlikely), these shouldn’t take much space, so it’s not really a concern.

Get the 32GB one

As you can see, even if you have little music, you’re really quickly going to hit the 14GB of free memory the 16GB iPhone 4S offers you (that’s what you’re really left with after iOS is installed). Therefore, unless you want to have to worry about it, you’ll be safer getting the 32GB one. This is higher than what we recommend for the iPad, because we believe the iPhone is much more of a camera and music player.

AT&T, Verizon or Sprint?

There are three parameters to take into consideration when you pick a carrier; price, speed, and coverage. Whichever carrier  you go with, you’ll be able to roam internationally thanks to the fact that the iPhone 4S is a worldphone, so that’s not an issue anymore. As you’ll see, it’s all about coverage.

Price

The first variable, as you can see in the chart comparing prices below plays little role, as the difference between the most expensive carrier (Verizon), and the cheapest one (Sprint), is about $10 a month, which isn’t significant you’ll admit.

Yes, Sprint does offer you unlimited data, but you’re not likely to need it so don’t let that lure you in. That is, since you can only use the data you have on your iPhone (and tethering to a computer comes at an additional cost), if you’re like 95% of users, you won’t need it. If you’re not, you’ll know about it and you can always change that later.

Speed

One important difference between AT&T, and Verizon or Sprint is that AT&T uses the GSM standard while the two others are on CDMA. The difference is mostly that GSM has received more improvements, which the iPhone 4S can take advantage of, and the data connection will be very noticeably faster. That is, when the network is good, an AT&T iPhone 4S (and even 4) will be orders of magnitude more than twice as fast to download an email, an app, music and so on thanks to HSPA+. If you’re not planning to surf much on your iPhone outside of your home wifi, then you might not care, otherwise, it’s important to consider that.

Coverage

Coverage is a tricky thing, as it’s really hard to find out up front whether you’ll have good coverage where you care about it. The general rule is that AT&T and Verizon have the largest coverage, with Sprint being more present in cities, but less so outside. Then, AT&T is considered less reliable generally, but your mileage may vary.

Our advice is to see for yourself. Think of the places where you’re going to need your iPhone the most, and ask people around you, friends or neighbors how their phone is doing. Honestly, this is the best way to go about it. Further on, don’t forget that you can generally return your iPhone for a short period of time, so if the coverage is bad at your home or office, don’t hesitate to send it back and try another one.

All in all, our favorite is AT&T because of its average price, wide reach and faster speeds. Exception: New York City and San Francisco users might want to try Verizon first, as there are a lot of users on AT&T there already.

Conclusion

My recommendation would be to go with a 32GB Black iPhone 4S, which retails for $299 with a 2-year contract. It might be a $100 more than the entry price, but don’t forget that owning an iPhone will cost you over 2500 dollars over the next two years if you consider the plan.

Without a doubt, having some extra storage for pictures and music is really worth it on a device that is always in your pocket.