I think you'll find it is a requirement in SW that they had been through the programme themselves and reached and maintained their goal weight. Not sure about WW.
Don't get me wrong, I have nothing against SW just a leader who keeps saying how good it is but is not an example to it. I have heard of three others who friends have been to but not been impressed with the size of the leaders. WW leaders also have to get to gold but keep it off. This does not seem a requirement of SW leaders, according to my experience and three friends. I am sure if either plan is adhered to one will lose weight.
I've had two, one was overweight, one wasn't and had reached 'target'. I found the one which was still trying to loose weight actually the better consultant. She was friendly, encouraging and forgiving. I lost much more wight with that consultant than the skinny one scowling over her coffee at us all.
What does it matter of their size, or where they are with their weight loss if they are able to help you achieve your goals?