I perfer a gentle recovery ride unless I'm so physically destroyed that I won't be able to ride safely. For example, last year I burned myself out on one particularly difficult ride and the next day, when getting ready for the recovery ride, I couldn't find my helmet (despite just having it in my hands a few seconds earlier) and could barely keep my balance to throw my leg over the top tube. Additionally, I wasn't hungry and had a hard time forcing myself to eat breakfast or drink before getting ready for the ride. These were an indication to me, that I needed not to get on the bike.