It should be fine as long as you're not the type who downloads hundreds upon hundreds of apps. Most of the content that takes up the most space tends to be music, videos and photos, which can all be stored on the microSD card.
I might have to get the 920 for more space. But the 820 is only $50. Decisions decisions. Lol
Well. Then again. You are on AT&T, correct? How is it going to affect your plan pricing, were you to get 920? In the end it's not that big sum to dish out on a device that most likely will tide you for (maybe) two years, is it? Then again, you can always get a SD card for 820.
Wait until Black Friday. If you can score the 920 for $1 or one penny, then the only thing stopping you would be whether or not you can handle the physical size of the 920. If the 820 ends up being the cheaper phone to get no matter what, then get the 820. Just go easy on installing apps, I guess. You'll have the SD card for the big files.
I looked at both the 920 and 820 and for me the size and shape of the 820 was more appealing. I also like that it has a SD slot and removable battery. But to be honest they are both very nice devices can't go wrong with either.