How can one determine which of the websites followed by mosques in the city of Vitoria, Spain, is the most accurate in determining prayer times, especially given a difference of half an hour or more between them for Fajr and Isha prayers?

Allâh has obligated prayer upon His servants at specific times. It is permissible to emulate a just muezzin who is knowledgeable of the prayer times. And whoever emulates an Imâm at prayer time, their prayer is valid. It is preferable to adopt the opinion that avoids disagreement, such as performing the ‘Ishâ’ prayer promptly, and delaying the Fajr prayer until one is certain that its time has entered. So, whoever doubts the entry of a prayer time should not pray until certain, or until reasonably sure, that its time has entered. Avoiding disagreement is desirable as long as it does not lead to something forbidden.