Within Theravāda tradition, what are the differences in doctrine and practice between schools and sects around the world?
It appears that some teachers and traditions are more focused on samatha and jhana like Pa Auk Sayadaw and Ajahn Brahm.

And then there are other teachers and traditions that are more focused on vipassana like Mahasi Sayadaw, Ledi Sayadaw, Sayagyi U Ba Khin and his student S.N. Goenka, Ajahn Tong Sirimangalo and his student Yuttadhammo.

Samatha is cultivation of concentration and vipassana is cultivation of insight. 

Ultimately both are needed.