This may be old news, but I recently purchased a pair of the C751s for my wife since she really liked my C700s. I had read the only difference between the two were the case and shorter cable/extension cable that came with the C751s.
When I received the C751s, I immediately noticed the cable was thinner, both at the earpiece end as well as where the 2 channels are combined. The C700's cable is much sturdier and I suspect, will last longer. I listened to the C751s after several hours of burn-in, but felt the sonic signature was the same, so it appears the earpieces are identical. There is a cable slide on the C751 which is not present on the C700.
Buy the C700s if you want a sturdier cable as well as the tangle free design.
When I received the C751s, I immediately noticed the cable was thinner, both at the earpiece end as well as where the 2 channels are combined. The C700's cable is much sturdier and I suspect, will last longer. I listened to the C751s after several hours of burn-in, but felt the sonic signature was the same, so it appears the earpieces are identical. There is a cable slide on the C751 which is not present on the C700.
Buy the C700s if you want a sturdier cable as well as the tangle free design.