This really needs to be more specific as to which market data you are particularly interested in. Historical/real-time? Prices, quotes, earnings, ratings, news? For prices - every tick or OHLC bars such as 1-second or EOD? In my own projects, I'm now phasing out any IBKR API market data as a single source since for my purposes (perhaps quite specific ones, admittedly) they time and again proved to be somewhat unreliable, but even then it would be hard for me to give Polygon, which I also use quite a bit, a blanket recommendation because while their data quality seems mostly beyond reproach, some of their services require a lot of incremental labor in my project to be made use of, all the while coming at a pretty steep price. But then I guess compared to Bloomberg Terminal everything must be kind of cheap.
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Best,
DS
