It's mostly a matter of trust - Do you trust Swan or Binance or anyone else to send you your coins when you want them? Some would say Swan is more trustworthy than Binance, and hence worth the premium. Personally, I have never had any problems with Binance. With one caveat, when withdrawing coins from Binance the fee is pretty hefty, and for no good reason at that. So if you're not buying lots, the withdrawal fee alone may end up being much higher than the 1% from Swan, assuming they don't charge anything.
All in all it's about total cost and trust. The choice is yours.