I either one without the other is diminishes the experience. If I had to choose, I'd go with BBBJ, so long as I do get to cum. Failure there really sucks. I also agree with Blueman, The big difference was that some were really good at it and some were terrible. A bad BBBJ is worse than a fuck, a good one is better.
Hard Idle is also correct, having to pay attention and pull out also diminishes a good bbbj, the change must be smooth.