Depends on whether you'd spend a little more time walking or a little more time on the subway.
If you'd rather spend more time walking, just take the 6 train down to Spring street and walk west until you get to Hudson (15 to 20 minutes). I live very close to the 6 train Spring stop, so if you want to walk over together you can give a call.
If you'd rather spend more time on the subway, the way that gets you closest is to take the 6 train NORTH to 51st street, then hop on the E and get off at Spring (different Spring stop). Walk a couple blocks west and you are there.
Yet another way would be to take the 7 east to Times square, take the 1 or 9 down to Canal, walk up Varick to Spring, take a left, walk one blick and you are there. This is the compromise between extra subway and extra walking time.
Edited because I have a knack for saying east when I mean west.