You can go to Samsung and find the different specs for each carrier. Do a search for Galaxy Tab and you should find the site. The biggest difference listed (other than the networks), is the amount of internal user memory. If I remember correctly (don't rely on my memory, check for yourself), T Mobile offers 16 GB of internal memory and no micro sd card. The others have 2 GB internal user memory and a 16 GB micro sd card. AT&T wasn't listed.

 

I went with VZW. They waived my ETF on my Mifi, eliminated the line for me and now I use the Tab as a Hot Spot. No Contract FTW.

 

In my opinion T-Mobile got the best Tab... 16GB INTERNAL storage and you can't beat the T-Mobile data pricing... $39 for unlimited SMS/MMS and 5GB of data... Unlike the other carriers, once you reach 5GB of data on T-Mobile, they do NOT charge you extra.... They simply state they *might* throttle you down from 3G to EDGE for the rest of that billing period...

As an added bonus the T-Mobile version has NO crapware that the other carries added into their version...

More internal memory, and a no overage data plan for $39.... Yup, I went with the T-Mobile version.... It's a no brainer IMHO...

 

I would not buy a VZW or Sprint model. I would only use GSM. And I would check to see which one is carrier unlocked and has compatible frequencies with the rest of the world. And this points to AT&T.

I see from your screen name that you are Vietnamese. Well, I just came back from an overseas trip to Vietnam and I was able to use my Captivate (AT&T) Galaxy S (unlocked and rooted) and my Ipad in Vietnam using Vinamobile 3G. It was awesome. I paid around $8 and I had 3G service for about a week and a half. I also had my Verizon MIFI with me and guess what, there is no CDMA service in Asia. So maybe my experience can tell you something.

BTW, you can get USB 3G dongles in Asia for like $20. If you get tired of your Galaxy Tab (GSM), I guarantee you, you can easily sell it abroad and make a nice profit. You don't even have to leave the country. Put it on ebay w/ Intl shipping and it is guaranteed to be sold and maybe make a profit/minimize your loss.