In Single Mode you do not care in the least which tuner is used to record.
If I use single user mode is that an even better choice for me? Is that where PIP comes into play where I could swap tuners say tuner 1 is stuck recording something, I could PIP swap and watch an HD program using tuner 2?
Take a simple case. You have one timer set for 8:00 PM-9:00PM tonight. At 8:30PM you turn your TV on (with your 622 in Single Mode.) If you want to change the channel you are viewing, just do so. The single scheduled recording will simply go on in the background on whatever tuner you are using and you will view on the other tuner. The choice of which tuner is being utilized for recording becomes a non-issue in Single Mode.
Disclaimer: If you are recording OTA, that fact is important in either Single or Dual Mode as you can not simultaneously view a second live OTA station owing to the fact that there is only one OTA Tuner.