what are the advantages and disadvantages of formal and informal service

What exactly do you mean? Are you asking about the Hospitality industry or for dinner parties? Either way, they both have their advantage and disadvantages. From a professional standpoint: FORMAL ADVANTAGES high profit higher chance of repeat business less marketing required (more word-of-mouth recognition) more leeway with creative ingredients/techniques FORMAL DISADVANTAGES high initial outlay requires constant updating and maintenance to stay relevant requires high-calibre (and expensive!) staff extremely high wastage INFORMAL ADVANTAGES higher turnover more guaranteed business less pressure more opportunity to use offcuts/leftovers INFORMAL DISADVANTAGES less recognition likely to attract lower quality/temporary staff more work for less profit I hope this helps, and I hope I'm not answering an entirely different question to the one you're asking! :)