Different brokers are linked to different sets of banks to complete their transactions so there will always be some variation.
However every I have compared different brokers in real time and there is usually not a lot of difference between the major brokers in the same markets. The more difference between brokers, including size of their connections and geographic area, the greater the differences.
This is only true if you are using live accounts. DEMO data is filtered by brokers and not updated as regularly as LIVE data. (Read the tiny, tiny print or ask your Broker about the difference between Live and Demo data.
Good luck.