I don't ride BMX, but I turn pedals just the same. Yes you can absolutely feel a difference between a 52:26 and a 34:17. At higher power levels the difference is more obvious, so I often try to stay in the big or middle chainring as long as I can and drop to the smallest 'granny' gear only when I am out of other options. I believe this is because of two reasons - a smaller gearset puts more tension in the chain, and the chain links must move through a tighter angle coming off of and going on to smaller gears than bigger ones.

But, as mentioned above, depending on the type of riding you want to do, clearance is more important than efficiency.