When does WP ping ?

I have http://rpc.pingomatic.com/ in my WordPress settings box, but I was looking on the technorati site and they say you should use, http://rpc.technorati.com/rpc/ping

Does anyone know which is correct?

I was also doing a search on technorati for my blog and nothing was found. Why is this?

I have been getting lots of spam though so it’s obviously being found by something.

Thanks