I've been to both at night, went in large groups though but never felt in danger. Go to a lot of baseball and hockey games at night as well and feel completely safe.
The Queen in ESTL is a little worse but plenty of security. The one thing they offer gamblers is a non-smoking environment. For me that's a real nice feature, but the pathetic 2x odds on craps usually keeps me away.
All in all, I do agree, Ameristar and Harrah's by the airport are in much safer environments. I don't play slots much, so can't comment. Yeah, Ameristar certainly is way ahead of Harrah's as far as customers ever since they built that new night club.