Ahh...the old heat gun vs hot plate argument! This is a question that each tech will feel differently about. I have personally done replacement screens on hundreds (thousands?) of iPads using a heat gun. I like being able to control which part of the screen gets heated up. Also, usually the iPad will cool down before you get all the way around. That means a hot plate will actually take make longer since you have to keep reheating the device.
The short answer is: Do what works for you. I love my heat guns and would never give them up. To me, technique is much more important than the tool in this case. Some techs will swear that their hot plates are better than any heat gun out there. Use whichever one allows you to work the fastest while delivering the best quality.
And buy some D-Limonene to get the glue off. Trust me on this one.