I'm a user of both TD Ameritrade "TDA" and Interactive Brokers ("IB"). Some considerations for you if you're deciding between them.
One bug bear is TDA account opening takes a long time (about 1.5 months). So far, my experience on email responses have been pleasant and they're prompt. Like recently, I wrote in to them about the delayed data and few days later, I saw that they've activated realtime data for me.
I like the Thinkorswim interface, which is so much easier to use and cleaner-look than IB's Trader Workstation. Honestly, their strength is for options trading.
Also when you fund the account, they convert SGD>USD automatically. It's not something I fret about, but I prefer to convert the currency myself which IB allows you to do that.
In addition, if you want to do custom statements (e.g. generate a report on your options trading for each month, which I do), I don't think TDA has this function. Meanwhile, you can do that in IB portal (which is buggy - every time the timer hits 12 midnight, they will tell me to activate Realtime Communication, like whatever that means...bruh. In the end, I'd just go to Trader Workstation to put in my order 🙄).
As for fees, TDA wins hands down for most parts.
- $0 commissions on stock, ETF and option trades
- USD 0.70 per option contract.
If you trade OTC stocks (which I have in IB), there's a USD 7.44 commission vs IB USD 1 commission.
Both have their merits and shortcomings. Personally, I use IB more, as I have AU & OTC stocks. Meanwhile, I use options in both IB (using options to reduce cost of current investments) and TDA (options trading).
If I've missed anything out, please feel free to check.