Written by  Lance Ulanoff

The arrival of the Verizon Apple iPhone 4 has been cause for some celebration among Verizon customers and even some who are already using the phone on AT&T. In fact, virtually every smartphone customer is likely wondering if they should adopt one of the leading smartphones on the U.S.’s most reliable mobile network. These 12 facts may help you decide.

1) The Verizon iPhone is No Thicker or Heavier than the AT&T Model

Apple told me and my examination proves that these phones are like twins (more identical than fraternal). Both iPhones are 9.3 millimeters thick—still among the thinnest smartphones on the market.

2) The Antenna Design is Different for a Reason

It’s no accident that the AT&T iPhone 4 and Verizon iPhone 4 antenna bands (around the phones) do not look exactly the same. The differences are hard to notice unless you hold the two phones side-by-side—as I did. The Verizon iPhone uses a CDMA network antenna. In fact, it uses two CDMA antennas (a necessary redundancy for the CDMA network). As a result, there are identical antenna band bar breaks on either side of the phone. By the way, Apple told me that, unlike GSM, the CDMA network actually works to give you a few more seconds of connectivity before the call breaks off completely. In other words, even on the worst connections, you may still be able to recover the call. I never had a bad enough connection to see this in action.>

3) Death Grip is Hard to Find

No matter how hard I gripped the Verizon iPhone—or in what configuration, I could not recreate the old AT&T iPhone 4 Death Grip—that is unless the connectivity was already weak. So on the very rare occasions that I dropped down to two bars (which means I was in 2G land), I could cover all the antenna gaps and get the bars to drop down even further. Still I never cut off the signal.

4) It has a Personal Hot Spot

There aren’t a lot of differences between the AT&T iPhone and the Verizon model, but this is a biggie. You can turn the phone into a Wi-Fi hub for up to five devices. In my tests, the connection was strong and held on for at least 25 feet (One of my tests involved leaving the iPhone on a Windowsill and connecting through my Blackberry Torch from a room upstairs and on the other side of my home). Data throughput performance on the iPhone itself does diminish a bit when it’s sharing.

5) Data Will Cost You

As much as I love the personal hot spot—and I really do love it—it will cost an additional $20 a month with, for now, unlimited data for an additional $30 a month. That’s pretty pricey when you consider you’ll also be paying a monthly service plan fee. However, if you consider what you’d pay for a separate EVDO modem and the monthly data costs, you might actually come out ahead.

6) You Can’t Do Voice and Data at the Same Time

This is probably the single biggest limitation of the Verizon iPhone and could turn into its most popular complaint. You can make a call and you can get your data connection, but do not try and do it at the same time. For most people, this will not be a problem (how often are you calling and browsing the Web at the same time?). In fact, if you receive a call while using the Personal Hotspot on a 3G connection, the Verizon phone will prioritize the call. Interestingly, on a 2G connection, the call will go straight to voicemail.

7) AT&T and Verizon offer Virtually the Same Voice Plans

If you’re trying to decide between a Verizon iPhone 4 and the AT&T model, don’t base the decision on the calling plans. Both have $69.99 unlimited calling rates and, at the lower end, offer 450 minutes a month for $39.99.

8) No SIM card

Another physical difference between the AT&T phone and the Verizon iPhone is that the latter lacks a SIM card slot. CDMA phones don’t use SIM cards, instead relying on a cloud-based set of serial numbers to authenticate network phones. So you won’t be transferring this Verizon iPhone to another CDMA network unless that network—perhaps Sprint—decides to start authenticating Verizon’s CDMA iPhones. (PCMag’s mobile expert Sascha Segan told me the customer support headaches that would attend this decision make this possibility highly unlikely) Since we expect most people to be very happy with Verizon, this doesn’t seem like a big deal. Sprint customers, of course, may disagree.

9) General Availability Comes on Feb 10th

By now you’ve probably heard that Verizon sold out of the pre-order inventory of Verizon iPhones. Apple did tell me that the phone would only be available in “limited quantities” to existing Verizon customers. It’s unclear what supplies will be like on the 10th. Also unknown is when, exactly, Verizon will start shipping those phones.

10) Verizon and AT&T 3G Are Both Fast

There’s no question that AT&T’s 3G network, once America’s fastest mobile network, is faster than Verizon’s 3G, but, as I can attest, it’s only faster when you can get it. Verizon is fast, too, and I doubt most people will notice the difference even when both networks are operating for you at peak speeds. I certainly didn’t. What it comes down to is coverage. I had better coverage overall with the Verizon iPhone, which means that even if there were moments when my mobile data network wasn’t as fast as the best I could get from AT&T, I knew that at least I could get connected from virtually any location. This was never the case with the AT&T iPhone.

11) Your Old Bumper Won’t Work

If you bought a bumper for your AT&T iPhone, you may want to throw it out or leave it on the AT&T model when you pass it along to your nephew. Apple moved the volume buttons a few millimeters and the hold button a bit more. The new Universal Bumper will work on your new Verizon iPhone and the old AT&T model, as well.

12) Don’t Wait for iPhone 5

While there’s no guarantee Apple will introduce this now much-talked about vapor-phone, it’s a safe bet it’ll arrive this summer. That said, when it does arrive, it will be in short supply. There is also no guarantee that the iPhone 5 will launch on multiple carriers—most smartphones do not. What if Apple starts with AT&T again? Won’t you feel silly for waiting?

Bonus:Naturally, the common people don’t want war…