There is a comparison with some employees considered themselves seriously, but some of them do not work, only to dump him (maybe there may be barriers or conditions of work that we do not know).
A comparison between staff Some groups believe that their work seriously. However, some groups did not throw as much as he. (Perhaps a drawback or working conditions that we do not know).
A comparison between employees. Some groups consider their job seriously. But some groups don't throw as him (maybe there are obstacles or working conditions that we don't know) .