Tomorrow, June 21, the Samsung Galaxy S3 arrives in the United States. A carpet bomb launch will see the phone arrive on all four major carriers — AT&T, Verizon, Sprint, and T-Mobile — at the same time, at the same price ($200 for the 16GB version, with a two-year contract). Verizon, Sprint, and US Cellular will also offer the 32GB variant for $250. But which carrier is the best choice for the Galaxy S3?

Fortunately, as you may have noticed, Samsung seems to have pulled off the impossible and convinced every US carrier to call the Galaxy S3… the Galaxy S3. For the time being at least, we won’t be seeing the same hyperbolic noun treatment that previous Galaxy S phones went through (Fascinate, Vibrant, Epic 4G, Epic 4G Touch, etc.) This has the knock-on effect that almost every Galaxy S3 available in the US will be virtually identical — at least hardware-wise.

Every US Galaxy S3 has the same Snapdragon S4 MSM8960 dual-core 28nm SoC, clocked at 1.5GHz, with the Adreno 225 GPU. They weigh the same (133g), have the same battery life (around 9 hours), have the same 2GB of RAM, and most importantly, they all have Qualcomm’s awesome multi-mode 2G/3G UMTS & HSPA/4G LTE radio. The only difference as far as we can tell is that the T-Mobile variant (SGH-T999) doesn’t support LTE, and the AT&T/Verizon/Sprint models (SGH-i747, SCH-i535, SPH-L710 respectively) don’t support T-Mobile’s HSPA+. We believe the Snapdragon S4’s radio might be reconfigurable with some firmware hacking, however; it might be possible to take a T-Mobile S3 and use it on AT&T’s LTE network.

All US Galaxy S3 phones support Bluetooth 4.0 LE, 2.4 and 5GHz WiFi a/b/n/g, and NFC. Except for the Sprint variant (SPH-L710), it is likely that all Galaxy S3s are quad-band GSM and should be capable of GSM roaming in Europe and Asia.

As you’ve probably guessed by now, the main difference between the Galaxy S3 on each carrier is bloatware. While all of the carriers’ S3s will have Samsung’s fancy new apps (S Voice, AllShare Play, Media Hub, etc.), each carrier will have a different selection of bloatware on offer. The Sprint S3 will come with the usual Sprinty stuff (Hotspot, SprintZone), plus Dropbox and Google Wallet. The AT&T S3 is relatively svelte, with just the normal AT&T apps (Navigator, Messages, myAT&T) and YP Mobile. Neither the Verizon or T-Mobile S3s have been released for review, so we won’t know how bloated they are until they arrive on our doorstep tomorrow.

All Galaxy S3s will run Android 4.0 Ice Cream Sandwich, skinned with Samsung’s TouchWiz.

Except for bloatware, then (which you can easily remove), any Galaxy S3 purchased from a US carrier will be virtually identical. There are still two very important variables to discuss, though: Network speed, and the international quad-core Galaxy S3 (GT-I9300).

While the US Galaxy S3 is an LTE phone, there isn’t actually a whole lot of LTE coverage in the USA. Fortunately, our sister site PC Mag has just published its Fastest Mobile Networks 2012 guide. While Verizon is the overall 3G/4G winner, there were still 11 cities where T-Mobile’s HSPA+ network provided faster download speeds than Verizon LTE, and where AT&T LTE is available it simply blows away the competition.

Bear in mind that Sprint’s 4G LTE network is almost nonexistent (though its Network Vision upgrade is underway). T-Mobile is also beginning to roll out LTE (alongside HSPA+), though again you will probably have to hack the radio firmware to be able to use it.

Before you pick a carrier for your new Galaxy S3, I strongly suggest you check the 3G and 4G speeds for your city or region.

Finally, it’s worth remembering that you can also buy an unlocked, off-contract international (i.e. non-US) quad-core Galaxy S3 (GT-I9300) for around $800. The GT-I9300, with its 1.4GHz Exynos 4 Quad and Mali 400 GPU, seems to clock in significantly higher scores in GPU benchmarks, JavaScript benchmarks, and CF-Bench (a multi-core CPU and memory benchmark). Battery life seems to be roughly the same, but the Exynos version only has 1GB of RAM vs. the Snapdragon’s 2GB.

If you don’t like bloatware, it’s also important to note that there’s already a CyanogenMod 9 (i.e. vanilla Ice Cream Sandwich) build for the GT-I9300 — though I’m sure it’ll only be a matter of days or weeks before we see CM9 for the SGH-i747, SCH-i535, SPH-L710, and SGH-T999. The GT-I9300 should work on AT&T’s HSPA+ network, but it will be incompatible with T-Mo, Verizon, and Sprint.

Read more of our Galaxy S3 coverage, or read our LTE explainer.