pater design for qthread manager

[Talei]

It's educational question and not a problem per se.
Currently with i7 Core we have 8 thread's and some people would like to do, lets say 2 things at the same time, so I want to implement in my app. how man thread's can be used so one can utilize 100% of cpu or do "background" operation with only 1 thread / core. (I already did implemented that, with option that detects current CPU threads count)

I read about QThreadPool that's why I ask here question regarding opinion. (maybe for another ideas to)

Why using QThreadPool is beter then QList<QThread > approach? With QList I run test with many threads and everything works fine.
IMHO this is similar although I don't know how this compare performance wise.

EDIT:
Situation in with I will use this is:
I have i.e. 2k jobs, those jobs use 100% core each and can be performed in different amount of time. So with Core i7 we have 8 threads, with C2D 2 thread's etc. So I need to create n threads to run n jobs at the same time. But I want have an option to use only 1 core so I can, i.e. browse www. I don't want to delete qthread and class that I move into it because it will be reused for the next operation to maximise performance.