In my limited leymans knowledge of this I would say that I cant see the benefits of adding 30lbs of fat, v's adding 20lbs of fat, if it is not bringing much more muscle with it.
I think it is very highly dependant upon the individual. For exampl someone that is near their genetic potential, or older (as metabolism works differently as you age) would not see the benefits of an all out 'eat as much as you can' bulk as there is only finite amounts of muscle that they can build, therefore they would be better off (c)lean bulking, otherwise come 'cut' time they are just going to have more fat to lose and the chance of losing muscle is greater, putting them either back to where they started, or worse with less muscle.
Now if you are a fair bit off your 'potential' then I think you can aggresively bulk much more productively as OK you will be gaining fat, but you will be gaining muscle, hopefully, just as rapidly (well not AS rapid, but you get my drift). Plus if you are younger the body is more efficient at making muscle (i think) and so more of those calories will be turned to muscle, than someone 20 years older who may just gain fat. Then when it comes to cut time, as long as you do it slowly you can hold on to more muscle...
If you are older AND way of your potential, then i think somewhere in the middle would suffice, as you wont be as effective at making muscle, but as you have more muscle to potentially make you have more room for the growth if that makes sense.
Just my veiw, but i could be way off the mark...