There is a lot of good trading multicharts interactive brokers forex margin out there and I have not independently tested every one of them to accurately compare them. However, I have tried a bunch of them so I can give you some of my thoughts and some things to look for.
In many cases the trading software you pick will have a lot to do with the broker you pick so we will look at them together. Portfolio margin can give you up to six times the buying power, particularly for selling naked options. Cash accounts that re-use uncleared money are in violation of the free-riding rule or may have done a liquidation violation which may cause his account to be restricted for 90 days if it occurs 3 times in a year. Stocks take 3 days to clear and options take 1 day to clear. This rule might not be applied by some brokers on an option trade that is simply a rollout to a later expiration. This limit is not that hard to reach for active traders of stocks who have a robust list of favorite go-to stocks to find good trading setups or for those who subscribe to multiple stock pick sites that give long lists of potential setups. Tom Sosnoff, who is a great options trader.
As such, the TOS platform is outstanding for options trading. The 32-bit version has a limit of 1. The 64-bit version will allow much higher memory usage. The TOS platform is good and attractive looking, but it has some difficulties scaling up without some fine tuning and has very limited 3rd party trading software tools support. They have the highest level of 3rd party software support of any trading platform. Their data is excellent and there is no hard limit on the number of symbols.