First off, you won't get AT&T LTE support with the international version, or with any other version. With that said, there are things to consider between the international version compared to AT&T version in terms of the hardware.
The International version is a quad-core version, no LTE support, but it DOES come with a FM radio receiver. The big down side, it only has one gig of RAM, which can be problematic if you tend to run a lot of apps and don't close them out regularly.
The AT&T version supports LTE, is dual-core without the FM receiver, but has the 2GB of RAM.
The bloatware really isn't a big deal, and because we have Ice Cream Sandwich, you have the option to disable the bloatware you don't want, even if you can't uninstall it. Now, the issue of software updates should be negated once Jelly Bean comes out for the AT&T version since 4.2 will PROBABLY be skipped. Key Lime Pie hasn't been talked about much for a while, so who knows what is going on with it. Also, if it REALLY makes a difference, you can always install an unofficial firmware update(rooting and installing a "ROM") if it becomes too big of a deal. The question remains, when will AT&T and Verizon release Jelly Bean? It SHOULD be soon, so you will probably only have a week or two wait if you picked up the phone on Friday(after the holiday).
I personally will stick with the official software on my AT&T Galaxy S3, at least until after Jelly Bean comes out for it, and until there is something really compelling about what is out there with 4.2 or later that makes me jump the gun on a possible official release of THAT. From what people have said, 4.2 looks to be more about updating stock Android to include things that Samsung included as custom stuff already, which is why it may be skipped on the official updates cycle.
I hope this helps.
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