complete rest or recovery run

I'm training for a hill marathon and did a killer  2 hour 15 minute session yesterday, including 1,000 metres of ascent and running the downhills as fast as I could.  My quads are completely pulverised today and my abs right under my diaphragm feel well exercised.

I had a recovery drink, good meals afterwards and an early night.  I'm in a dilemma - is it beneficial to run a very easy 4 miles today, or should I just rest? If I run, I do mean SLOW.