Odoo has two different templates rendering engine know as Qweb
one for server-side rendering and other for client-side rendering 

both used the similar syntax (t-if, t-foreah..) except template inheritance
server-side user xpath and client-side user jquery to for inherit template

You may probably get a better answer but from my limit experience, "t-query" or qweb is predominantly used in customising reports as it is HTML based https://www.odoo.com/documentation/12.0/reference/qweb.html 

Where as xpath is used in the forms and views https://www.odoo.com/documentation/12.0/reference/views.html