The number of classes of goods and services specified in a trademark application can have an impact on the chances for a successful registration, although it does not directly determine the outcome. The main consideration is the distinctiveness and strength of the mark itself, rather than the number of classes. Still, including multiple classes can introduce additional complexities and potential challenges to the registration process.
Filing in multiple classes means that your mark will be evaluated against a broader range of existing trademarks. The examiner will search for prior marks that are similar or identical to yours within each class. If there are existing registered or pending trademarks that closely resemble yours in any of the classes, it could lead to objections or refusals based on a likelihood of confusion between the marks.
However, it's important to note that the success of a trademark application ultimately depends on the overall strength of the mark itself, its distinctiveness, and its potential for causing confusion with existing marks. Including multiple classes does not automatically decrease the chances of a successful registration if the mark is strong, distinctive, and not likely to be confused with prior marks.