The biggest advantage of the EU Trademarks is the simplicity. You can register your trademark in all the countries of the EU with one single registration. The Trademark protection is valid in all current and future member states of the EU.
The protection is valid for 10 years and can be renewed indefinitely.
Another very interesting point is the price. Compared to other trademark applications in Europe fees charged for an Eu Trademark are quite low. Registration costs for national Trademarks will be much higher.
The protection and the value of your brands will be higher as if registered on a national base.
Nevertheless, given the nature of the multiple countries in the EU, trademark owners of the national trademarks may oppose against the EU filing. Means if a German trademark owner opposes against the EU filing, because of earlier rights, the EU filing might be rejected. Therefore it is very important to make an in-depth check before starting the registration process.