Should I use SQL JOIN or IN Clause?
In SQL Server, with a few assumptions like "those fields can't contain NULLs", those queries should give the almost the same plan.

But also consider the type of join you're doing. An IN clause like this is a Semi Join, not an Inner Join. An Inner Join can project onto multiple rows, thereby giving duplicates (compared to using IN or EXISTS). So you may want to consider this behaviour when choosing how you write your query.