Some say that gdax is too complicated and I should stick to coinbase for trading to fiat money.
Why is gdax complicated? Someone that uses could help me please, my concern if it is safe as well.
it's not complicated at all. because of the high fees on coinbase, i highly recommend GDAX.
it has a different interface than coinbase and allows limit orders and stop losses---that's about it. if you want to market buy or market sell like on coinbase, you can. it only costs 0.25% fees instead of coinbase's 1.5% fees. and you can use limit orders (orders that stay on the book until somebody fills them) with 0% fees. they offer free BTC withdrawals too.
coinbase is very simple and you don't need to worry about your order getting filled---they get automatically filled. for that privilege (and the convenience of direct buys from your bank account rather than depositing, transferring and setting orders), you pay ~1.5-4%. screw that! you can just transfer directly from your coinbase to GDAX account, set orders, and avoid those fees.
