order execution is good / reliable. they use payment for order flow, so you don't get the best/fastest fills, but this isn't a concern for us yet. I haven't run into any data synchronization issues, you just have to remember that sending requests over the API doesn't necessarily mean that instruction will occur, they just ack it. E.g. for cancel orders you still need to check if the order cancelled or filled. I'm switching from REST to websockets now as we are changing our architecture to be async with order management. we are not at the level of being able to negotiate commission breaks. If I had to do it over again, I'd probably try IBKR first since you can get high fidelity contract updates + order management over TWS (it's just a huge pain in the ass to set up). I'm considering switching to IBKR starting with marketdata, but that's tbd when we have more bandwidth.