Is the second conditional more polite than the first?

I have learnt that the difference between the first and second conditionals is a possibility: the former implies higher likelihood than the latter.

However, in spoken English, I hear the second conditional sentence more often, as in the following pair.

1. If I am offered the job, when will I start?

2. If I was offered the job, when would I start?

Does 2 sound more natural/polite? If so, is it because of the odds?