I really like the QS Defy 5W30 in my '80 Firebird FORMULA V8. It's made the engine smoother/quieter than any oil before it(and I've owned this car for 33 yrs).
I have used MaxLife 5W30 on the 3 previous/summers OCI's and will be going back to the MaxLife summer 2014 only because I got the ML on sale. But, I like the QS DEFY better. Both oils have slowed down my leaking/drips/make up qts.
I can't say that one is better than the other in the "slowing down the leaks" dept. But, the DEFY certainly makes this old Small Block V8...out of charactor smooth/quiet! Which I am finding to be true with other QS oils that I've been using in my daily drivers.