ITIL/ISO 20000 education

Answer:
It's hard to tell, that depends on many parameters, like context of your working environment/needs, why do you need that, what do you want to achieve, personal preferences, availability of training organization, professional path/ambitions, etc.
General, ITIL training encompasses more than ISO 20000, so it's also useful if you implement ISO 20000. On the other side, ISO 20000 training is ISO related, so you can use some logic for other standards as well.
Read the articles, to gain more information:
"ITIL Certification Path – list of all available ITIL trainings, exams and certificates" https://advisera.com/20000academy/knowledgebase/itil-certification-path-list-of-all-available-itil-trainings/
"How personal certificates can help your company’s IT Service Management" https://advisera.com/20000academy/blog/2017/04/18/how-personal-certificates-can-help-your-companys-it-service-management/
"New ITIL Practitioner Guidance book – what does this mean for your certification and implementation?" https://advisera.com/20000academy/blog/2016/08/30/new-itil-practitioner-guidance-book-what-does-this-mean-for-your-certification-and-implementation/
"Process to obtain ISO/IEC 20000 certification: Companies and individuals" https://advisera.com/20000academy/knowledgebase/iso-20000-certification-the-process-of-obtaining-a-certifica/