thanks for your enquiry. Here are my thoughts on the topic.
EAB’s exams reflect to a great extent a ‘traditional’ approach to language exams, using translation as a major component. Unlike traditional exams, though, EAB’s are available at any time and ‘open book’ – a candidate is given a number of days in which to complete the work, is allowed to use reference materials, but certifies that the work has not been aided by another person – so ‘running for the dictionary’ is fine!
The international ‘KER’ (CEFR) exams are good, modern and valuable as meeting internationally agreed standards. Of necessity they are exclusively in Esperanto – translation has no part in them. They have been less flexible in terms of administration and actually taking (the need to attend a specific location at a specific time), but recent experience with ‘virtual’ sessions may lead to greater flexibility.
Ii is difficult to compare such different exams, but I think that the level of language in EAB’s Elementary equates to high A2/ B1 in CEFR; Intermediate to high B1/ B2; Advanced to high B2 / possibly C1, but only just! It must be noted that CEFR/KER exams test all four skills (listening / reading / speaking / writing) at each level. EAB’s exams don't test listening at all - except as part of the Advanced speaking exam, within the conversation section; and only the Advanced exam tests speaking at all.
Whichever you choose (maybe both types?) – bonŝancon!