I always prefer to exchange currencies through exchanges and not through internal wallet swaps/exchange.
Ain't that the truth, even if you're talking about one of the more reputable "instant exchanges" like Changelly.
And beware at times like this when bitcoin is white-hot. This is when all the scammers start coming out of the woodwork to get their hands on people's money, especially newcomers drawn into the world of bitcoin precisely because its price is on fire. They're the ones who likely don't know all the things you shouldn't do--through no fault of their own; it's just their inexperience.
I've used the Atomic wallet before, but never any of their partners (which I'm assuming is what this thread is about). Nor will I. There are enough legitimate exchanges out there such that you shouldn't have to resort to using shady ones. I've done it for obscure altcoins that don't trade on the major ones, and I've often paid the price for experimenting with ones like HitBTC, Coinswitch, and a few others. It's not worth it.