Cheap (but good!) tablet: Barnes & Noble Nook HD+. 16GB for just $140. 32GB for $180. Comes with not just the curated market system from Barnes and Noble, but is actually NOW full Android OS. So you get access to Google Play and all their apps. Did I mention it also has a MicroSD card that will also auto-load a custom ROM that you could setup or download until a MicroSD card?
Now, with my B&N cheer out of the way. Stay away from Windows RT. The only benefit it has, and you would need to buy the newest and latest Window-based tablets, Outlook and work programs. But to me, tablets are more of a personal entertainment device. In certain situation and setups, it can function fine in a business or work environment. But overall general purpose, without having to sink extra money into peripherals and programs, it's an entertainment device.
Namely, you got four types or kinds of tablets to review and figure out.
1) Apple iPad. First to the market, they set the standard. Has a lot of apps, compatible with iTunes, etc. etc. Biggest con for me: Price is high; even their mini-iPads are high priced and the quality has dropped compared to its direct competitors (Kindle, Nook, Nexus). However, the new iPad coming out is supposed to address a lot of the faults.
2) Android-based tablets. Large variety of manufacturers. Personally, the biggest two to deal with is Asus and Samsung. To be fair, you can also buy the Google Nexus tablets, but I give credit to the other two for helping design and create the Nexus tablets' features and size.
3) Amazon Kindle. Amazon has just announced the new Kindle Fire HDX for just $230. Check out its features; Ridiculous for that price point!
4) Barnes & Noble Nook HD+. Now, this is an older tablet that came out about a year ago. However, it has a lot of pluses, namely it has quality and its a VERY low price compared to other tablets available.
So the main questions I think you should ask yourself:
1) What do you plan to use the tablet for? Work? Entertainment? Reading? Music? etc. etc.
2) What features are must haves, and what are nice additions to have? Preferences in OS? MicroSD or no? Keyboard peripherals? Screen size? etc. etc.
3) Price point. How much are you willing to spend. Remember, some of these tablets (cough Kindle cough) have additional features (Amazon Prime) that is included in the price, so you actually get two things for the price of one (Save like $80 on Prime).