I will say that purchasing from a dealer is also nice because if there is an issue, the dealers are much quicker to resolve it. For example, Charles RO has quickly done repairs for me when a new engine arrives with a pinched or disconnected wire.
I also like supporting local dealers that hire people in areas where I or my family lives (Boston, southeastern PA, and Indiana). I buy from trainworld because they do great outreach for our hobby, I support Mr. Muffins because he’s using his resources to help lift up his hometown, and Charles RO is luckily my local shop. When I pre-order I tend to spread the wealth since I like the folks. I also buy from Nicholas Smith, Henning’s Trains... the list goes on and on.
Point is, I buy way too many trains and accessories, and I like to support as many dealers as I can