Big box stores attract the home consumer (like myself) who's lawn maintenance needs are less than their professional or large land owner counterparts. If my needs were more commercial, I would definitely choose the dealer over the BBS. However, I am a small land owner and my needs are strictly consumer grade. And the BBS offers me the best prices for the consumer grade equipment I require.
I hold the independent dealer with the same regard as I would a sports pro shop. If it was something I needed professional quality, I would turn to the local pro shop and not Sports Authority. However, if it is the first pair of skates for my 2 year old. I will go to Walmart.