Yes you both can leave all coins on Wagerr website if you like. Advantage over Waves is the 2FA authentication for logging in. On the other hand, Waves is secure as well if you just write down the seed (string of words to open your wallet) on several pieces of paper, logout from your account, remove the login from the Waves wallet. Buying Wagerr tokens with BTC via Waves is the best way. Good luck & welcome to the party!
Just out of curiosity, is there a way to sent the coins back to the dashboard if one would decide that he doesnt wants to use waves desktop wallet anymore?