The converse is that you'll still end up with the popular tools if you ask people what their preferred tools are and why...
OK, so I'll offer something different.
During my first year at uni, I used to own an HP-48G+ which I loved for its nice keypad and the RPN interface, but the actual device was hopelessly unreliable and had an unwelcome tendency to let me down by throwing hissy-fits during assessments. I eventually got around that particular limitation by replacing it with a TI-89, which (although lacking keypad quality and RPN) was, and still is, a vastly superior device on many levels.
But since this doesn't answer the OP's question, here's my take on it in the light of years of experience since my university studies...
The best calculator for examinations is: NONE AT ALL.
You will get much more kudos for arriving at any kind of solution (however incomplete) if you can show how you started from first principles. Also, you might actually remember how to use these skills years later if you do this.
I would like to be able to say this is what I did, but it would be a lie. I was not a brilliant maths student, since I relied too much on gadgets to help me through assessments. However, I have since revisited the subject and learned how to do it with more insight, and now find a certain pride in being able to "do" maths with no more hardware than a sheet of paper, a pencil and my brain.
Oh, and FWIW, although I still have my TI-89, most of the routine mechanical calculations I perform these days are done on the RealCalc Plus app on my phone.