No downside. I've been using them for 15 or 20 years.

Shimano DA/Ultegra/105 chains now come with Shimano quick links. No more pins.

The correct KMC part for 11 speed shimano chains is CL-555R (reusable) and CL-555 (non-reusable). The difference is not apparent and I've reused the non-reusable versions many times.

I've had a SRAM 11-speed PowerLink install tight. It loosened up after a mile or so but I try to avoid them.

SRAM, KMC and Shimano all work with Shimano chains.


-Tim-