I've done my tablets research and figured there needed to be a thread where I recommended, based on that research, what tablets to buy. If I'm wrong about anything point it out, but I honestly don't think I am. I've looked at reviews and everything. Okay so:
For an Android tablet, don't settle for anything less than a Nexus 7 16gb for 200 bucks. It has a 7 inch screen and a maximum resolution of 1280x800. The next step up I would get is the Asus TF300T. At 350 bucks, it has a significantly larger screen and 32gb memory. If you really want to spend, the Nexus 10 32gb at 500 bucks is the most powerful Android tablet currently and has a maximum resolution of 2560x1600. While there is a Nexus 10 16gb at 400 bucks, it's really hard to find.
Right now for Androids, you want something with the Tegra 3 processor, or a Nexus 10. Except the Sony Xperia, it has a Tegra 3 processor yet doesn't perform well in the graphics department for some reason.
The Tegra 4 tablets should be coming out soon, and my recommendations may change at that point.
On the Apple side, if you're getting a tablet, get an iPad 4. Don't settle for a previous-generation iPad at this point, the iPad 4 is for example about twice as powerful as the iPad 3. The iPad 4 has a 2048x1536 maximum screen resolution and runs 500 bucks for the 16gb version.