Oxford English youtube channel evaluate 8 dictionaries and give Longman the best with 10/10 score.
The feature I like best is plenty of examples and you can listen to sample sentences as well. None other dictionaries has this feature.
https://www.ldoceonline.com/dictionary/talk

The runner up is Lexico, whose content is provided by Oxford University Press, the publisher of famous Oxford Advanced Learner's Dictionary. I, personally, don't like this one because you need to choose either British and American English which is quite tedious when you want to compare Br/Am accents directly.
https://www.lexico.com/definition/talk

If you want to access Oxford Advanced Learner's Dictionary directly see this 
https://www.oxfordlearnersdictionaries.com/definition/english/talk_1?q=talk

I have been using both Longman and Oxford online dictionary for more than 5 years now. Highly recommended.

Here is the link of youtube comparison.

https://www.youtube.com/watch?v=d7mc1_7E3gY