8 Bit or 32 Bit Microcontroller

your question is like: A bus that can carry max 8 people with 32 MPH vs a bus that can carry 32 people with 8 MPH, which one is better.

Even though the 32bit micros are the best in the market but still you will have to chose what is best for your application.

if 8 bit is running at 32MHz and 32bit is running at 8MHz, I would prefer 32 bit, because of its lower frequency, the power consumption is less and in the backgrounds I will have a less codes.

 

Next time you're asked a question which starts from "What is better", ask "what is your definition of 'better'?"

There are many considerations when choosing an MCU, and two things which are of the least concerts are "number of bits" and nominal MHz speed. These are marketing things. However, since hiring is done by technically-illiterate HR people, you have little chance to be hired unless you say these things are very important. In real life, the most important thing is periphery - in embedded world you can achieve better performance doing things in parallel, rather than pipelining sequential software threads.

As to the speed, consider these examples:

16-bit dsPIC33 running at 70MIPS doing FIR will leave most of the super-fast 32-bit processors in the dust because FIR is exactly the task it was made for,

Little 8-bit PICs have predictable command timing and can be used for fast big-banging. Since most fast 32-bit processors use caches and pipelines, you can no longer rely on command timing and must use a timer instead, and hence you will require a processor with 5-10 times faster nominal MHz speed to achieve the same result.

 

I think the interviewer is trying to determine whether or not you know anything about microprocessors. The answer is probably NOT "This processor is better because... yada, yada, yada." They are probably looking for an answer that describes the in-depth considerations you would make before choosing a processor, thereby demonstrating that you actually know something about processors that wasn't simply a quotation from one of your lecture notes or text books.

Well, at least I would be looking for that kind of answer if I was interviewing you. There are a lot of pretenders out there with glib responses to questions, but no actual knowledge or experience that is of any practical use if they are hired. I have no objection to on-the-job training (OJT), but I would like to know before hiring just how much time for OJT will be required. If you have zero experience and are looking for your first job after graduation, you need to find some positive things to talk about that emphasize your current abilities and strengths. Activities outside of school that are related to the profession you wish to pursue can be a positive indication: electronic hobbyist work at home, a summer internship, voluntary part-time work in an appropriate industry can be mentioned in addition to whatever formal education you bring to the interview table.