Which is a good/safe Online Trading Platform

Hi Guys,
I need your help in gauging & then shift if needed, to a right trading platform.
Presently I use HSBC InvestDirect and they charge $6.88 fix fee for any (stock, MF, ETF) Sale or Buy, irrespective of the total value to each transaction their fee is $6.88 and I feel it becomes too expensive when I buy a small qty of shares.

But frankly speaking I’m not sure if any other platforms have better pricing & features. Since I’m banking with HSBC, just started HSBC InvestDirect trading account without evaluating if that was rightly priced compared to any other option.

I seek your advice on this matter. And if at all I decide to switch from HSBC to any other trading platform will it cost me anything to carry forward all my investment portfolio from HSBC InvestDirect to the new online trading portal and hope it is safe to switch from one to another online traders.

Appreciate if you could guide me in detail to take this call for a long term prospective based on your experience and feedbacks.