When choosing between a national and an EU trademark, the answer depends on multiple factors. The first is the number of member countries you actually wish to cover, which then influences the price. Since the EU trademark is a bit more expensive than one national trademark, you can consider filing a trademark with one of the national IP offices. A national registration might be sufficient if you sell your product or service only in one member country.
However, an EU trademark simplifies the process if you plan to sell your goods and services in multiple member states or all over the EU since you have to file only one application instead of 27. Moreover, it is cheaper than filing individual applications in all member states.
However, please note that registering a trademark in the EU could be more difficult since the EUIPO will notify more trademark owners about your application, and they can then exercise their legal rights to oppose your application.
If an opposition arises, your legal representative should inform you about suggested next steps, success estimation, and price estimate. Sometimes, when an EU trademark application is opposed, the only option is to break the application into separate national applications and file these with the respective national IP offices.