I've used the U shaped tube overflow since I set up my tank. I never had a problem with it and it's never lost it's siphon. Some ppl have problems with bubbles accumulating at the top of the U, but if your return pump is strong enough you should not have that problem.
After cleaning the U tube, you must put a piece of airline tubing through it to the top and suck out the air to start the siphon, or drill out the top, put in a check valve with a piece of airline and start the siphon that way. Might be a little hassle there, but as I said, it's worked fine for me for over 15 yrs.