IB does not use the exchange stop facility for NYSE stop orders. While the election algorithm differs, they are broker held just like Nasdaq. From what I've been told this is done at the request of IB's institutional customers that don't want to tip their hand to the specialist. As for their Nasdaq stops, they work fine provided you properly understand the election algorithm used and take it into account when choosing your stop price. IMO with all those out of market prints on the Nasdaq, having stops elected based on bids and offers is a superior solution.