This is a bit tricky question to answer.. Few brokers would be very sweet before opening an account and making a deposit.
I have traded with INTFX, Alpari and Octa FX. I feel Alpari is the best broker. I never faced any issue like re-quotes, stop loss hunt issue etc in their account. ECN is the best account type they provide.. Even withdrawls and deposits would not take more than 24 hours.
Worst broker - OCTA FX:
Never open account with them. When you click on close orders.. for example with "Close profit 500$", as soon as you closed your order and if you go to days history the order would be closed with 100$ profit or even -100$ profit.
I opened multiple chats with their support, but they said their liquidity providers would provide the quotes and they do not have control over the final profit..
So dont think that issue is only with manually closed trades with Market execution..
I tried limit orders as well.. Octa FX changed the bebaior of limit orders.. When ever you place order for "Buy GBPUSD@1.35200" and once the order is executed you can see that your order is execute at 1.35100 or so. The only best thing with Octa FX is withdrawl and deposit happens in 5 mins.. But they will eat all your money.
You can go to forexpeacearmy website and check for more reviews.