[Vlad_the_Inhaler]

There is no such thing as a 'British' accent, so I assume the debate is between Received Pronunciation (the old 'BBC English') and US English.
It all depends on the whether the learner expects to use English with other non-native speakers, or with British, or with North Americans.
Since most speakers of English are not native speakers, and most of these have learnt RP, percentages suggest it is better for the majority of learners to learn RP.

The strange thing about RP is that, to many ears, speakers with a Slav or Latin accent sound a lot better than the native English speakers on the recordings.