The benefit of being first-named author is that it is acknowledged that you did the most intellectual work. The advantage of you being corresponding author is that you are the person responsible for any follow-up correspondence. If not stated otherwise, the first author is the person to contact.
for the sake of science evaluation transparency each author should declare percentage contribution to a given article. Then the citation count and the other scientometric metrics should be calculated as weighted ones. Then the order of author names doesn't matter and can be alphabetical.
In most cases, the first author usually does the most of the work as stated bu Ian. Although, there could be very few exceptions to this. As for the other authors, many factors come into with regard to the arrangement. The corresponding author is responsible for all communications regarding the paper both before and after publication.