Great question. For my PC guys, it doesnt really matter (I want them all lol) but if I had to choose a preference I would say Patches. Most auto's of your PC guy basically look the same (at least, they should), whereas a chunky patch can look totally different every time.
Having said that I do like getting SP cards as well, nothing better than having a 1/1, or even really low numbered parallels (less than /25, but prefer /10 or less), which is why I have been loving Totally Certified and Prizm (just got Markieff Morris GOLD) and now Select as well.
When it comes to my set collections (usually Rookie Auto sets), I love On-Card Auto's, so I guess that means there is only GU'd that I am not into.