Leaving Bitcoin on the exchange

I've started buying a decent amount of BTC each week and have decided, as l have a habit of messing things up, l would rather gamble leaving in on the exchange than worrying about keeping codes. If l get hacked or whatever, so be it.

So far l have just been using Coinbase but my question is please, which exchanges do think are the "safest" to spread the funds around or am l probably better off just leaving it all in Coinbase?

Thanks.