Right join is just left join with the clauses switched, so it makes sense to use left join consistently. Inner join is just a left join with a 'not null' condition. I prefer inner join for conciseness, but it makes sense to always chose left join for consistency. Full outer joins are rarely needed in my experience.

In any case, all the joins are just syntactic sugar over cross product. AFAIK SQL did not have the join syntax initially, you just did SELECT foo, bar WHERE foo.id = bar.foo_id