The best way to join in Linq

I was working with the first method below, but then I found the second and want to know the difference and which is best.

What is the difference between:

from a in this.dataContext.reglements
join b in this.dataContext.Clients on a.Id_client equals b.Id 
select...

and

from a in this.dataContext.reglements
from b in this.dataContext.Clients
where a.Id_client == b.Id 
select...