The basic composition of an advert is that it must contain an offer or a promise. in the Advertising domain, there are many types that you can come across. informative advertising (which in this case is more likely to contain an offer) is more likely to be centered on communicating the products/services with less or no emphasis on closing sales or conversions. This is more engineered to achieve brand awareness so that when persuasive advertising is employed, the markets are prepared and have heard of the product before.
persuasive adverting is more aggressive in nature. The message is configured to persuade.
Other times both elements are employed simultaneously but for that, to work a good balance is to be achieved and the trade-off understood ahead of time. The trade-offs may be in the way of time. If you want to carry out an aggressive campaign there is a decision to be made concerning time. If you want to achieve a certain sales target, it may mean a multi media approach with more funds invested or less funds invested but a longer period may be required. In short, apart from the Marketing Strategy upon which the sales copywriting will be made, there are other considerations and these will always vary depending on the circumstance of the client.