Road buzz is an annoying thing. Some say it is a mythical thing. It's a vibration through the bike frame of an aluminum bike that some people swear they feel and others swear doesn't exist.
Honestly, for the style of bike you'd get at that price range, you won't be riding for distances that would really matter as far as road buzz is concerned.
Bikes do get stolen, even when locked up. That's where having a cheaper bike is a benefit if you are riding for errands. All kinds of bikes get stolen all the time, from cheap ones to expensive ones. Never lock up a bike which would break your heart if it were stolen. (take it inside with you)
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson