We use the Halti leads and have had no probs with them (large size), our first lead was a leather one from crufts. It was a good lead ref it had clips on so the length could be varied (like the halti one) but the leather was way too thick and tough

I use horse leading ropes. They are cheap, soft on your hands and extremely strong. You can wash them when they get dirty, and they are very good for tying dogs up in the pub garden etc.