I use both, and from my experience, some orders do not get filled, and has a huge slippage on the stop market orders. Especially volatile stocks with wide spreads like nvda. You have to do the math, for the vol of shares I trade on nvda, the avg cost for the week using IB is around $60, about 250/mth. TD, free. But I do notice that I have bigger slippage, sometimes up to .30-40 on entries, and stops compared to IB. However, the overall performance on stocks that has slower moves, and tighter spreads, such as $aapl, not much of a difference. it is a toss up for now, but as you move into bigger shares, and volume, then you have to calculate if the slippage loss on a given stock is worth the commission free trades. For now, yes for me on nvda, since most of the time, I am looking for min. of 2-4 dollar move, and the .15-25 slippage in entries, are. usually 5-7.5 loss, but make up for it in the trade. Limit orders are decent, but market orders execution on TD is terrible. But as i said, I have never been able to accurately tell how much slippage, but some of the stop/market orders have slipped by .20-35 cents. If you have 100-200 shares, that's 35-70 dollars. Yes, I have seen such loss on a stop that is suppose to @b/e. However, Ib has some slippage on market orders, and stop/market. But it is usually .5-10 cents. Nominal. What I am thinking of doing is placing a bracket order .25-40 cents in front of my b/e limit order.
The only danger about using a limit order, if it doesn't get filled, you can face a big loss. Stop market, you will get filled, but not at the price you have it placed, due to the slippage. so, yeah, one of those things that we deal with. I can't help but to think the mm and the brokers benefits from this somehow, but there is no way to prove it. I think they use micro pennies to make profits, but probably make a killing taking in the diff between a spread, and the slippage, if they can slip it in there. Happy trading Everyone.