The one you work with now. However, it is possible that one or both will access tempdb or that one or both will reside completely in memory. It all depends on the amount of data and the query.

The biggest thing to remember is the table variables do not have statistics and will be treated by the optimizer as if they have one row, regardless of the actual number of rows they have. I have heard differently at times, but my experience seems to hold this to be true. Best to test for yourself.