"Best" and "worst" are subjective.

I brought a Shiftpod2 and a fucking AC unit and I thought it kicked ass. On the flip side, I know two guys that went to Burning Man with nothing but backpacks and I'm pretty sure they had more fun than me.

There has already been a TON of discussion about this already here on /r/BurningMan and over at ePlaya - It is highly recommended that you go visit, set up an account, and do some research. SO much info that has already been shared.

Some general thoughts:

• Search and research and read the forums!
• Kodiak brand canvas tents, and the ShiftPod are considered "top choice" if you have the budget for either. The Kodiak is much more affordable than the ShiftPod. Each has its own pros and cons (like any tent).
• You generally do not want a tent that has "mesh" windows, as the dust will not only gather on the mesh material, but it will also blow right into your tent.
• You can absolutely use an inexpensive tent from any of the large retailers and you won't die. Many folks have used $40-60 tents (over multiple YEARS) and had great Burns. (research and read the forums!)
• I used a generator+AC to cool my tent. Extravagant, expensive, kind of hassle, but it worked for me. It is one of many approaches.
• Many people use a "swamp cooler" to cool their tents, powered by either battery or generator. (research and read the forums!)
• Many folks build a "monkey hut" as a shade structure to go over their tent and living space. They are very easy to build and affordable and make a big difference in keeping your tent cool (read the forums!!!)
• Not quite on topic, but: I had read once that before/during/after setting up your tent, go introduce yourself to your neighbors and let them know you're not an asshole. I thought that was great advice and my neighbors last year loved the approach.