Selecting the best platform
The first thing you need to figure out is how you will trade because that will matter in looking for a platform that supports your requirements. If you for example are a high frequency trader, then you want a platform that have good interface and support for quickly entering and exiting trades.
If you are coding automatic systems your choice in platform is by far most crucial. You need it to have great backtesting functions, simulations and reports with key figures. Such as average gain/loss and percentage of winners and losing trades.
If you on the other hand are a swing trader then the importance of platform is not as crucial. For you it’s crucial you have a broker that does not trade against you. A so called Market Maker. You want direct market access with accurate pricing, tight spread and low commission.