I actually said nothing of the sort. I stated what RF can do, not what BuildCraft can't do. And yes, you can do all of those things with MJ. You just have to work through a Helper Gremlin and its deputies. And you give up direct access to your own power. And you have forced loss, even when you check how much energy is in your tank. It's like Schrodinger's cat, except even if the cat is alive, it dies a little each time you check on it.You make it sound like the BuildCraft Power Api prevents a mod author from inventing creative ways to produce and consume BuildCraft power. There is nothing in the BuildCraft power design that limits how a mod produce or consume power. Make a "big reactor" mod. Use MJ to power an Airplane. Add a battery.
The perdition in machines is the only "forced" element and that was an attempt to add game play to transportation as well. The idea was to add a problem that the player could solve by being creative with the pipes, gates and wiring. It asks the player to think before placing the pipes.
Was it the best way of doing it? Maybe not. A little bit of idle loss in a few machines becomes more of a gimmick when you have 3-4 RailCraft boilers running at 20% capacity in your basement. But I still think it is better than boring RF.
Forced loss in machines is fine. But don't harp on Redstone Flux not having lossy transmission - BuildCraft doesn't either. And we all know why - it's CPU inefficient and chews up a ton of time. It's actually a very solid design decision on BC's part to have the new pipes work as they do.
You can state that the forced perdition is the only "forced" element, and that's a really big thing, but hardly the only forced element. It's also the time trackers, power direction trackers, helper gremlins, and perdition calculators that bloats the API and makes it a bit intimidating. So it's not just "ease of use," but also a question of, "Do I want my tile entity to use 100 extra bytes in memory for a power API I never have full control of?"
Yes, you can do a lot of things with MJ. Nobody is going to dispute that. But it's also a walled garden, and you can't dispute that.