I am a so-called fickle pickle and I am on my 4th town... since 2013 when the game came out. I also tend to get bored when I have unlocked everything, grown the hybrids I want and the rest.
One suggestion I always read about, is having as much as the river going up and down vertically - it is much easier to fish that way. Like the other replies suggest, it depends what you want to have as your focus.
It used to be that gaining lots of bells from farming island beetles was my thing in choosing a map, so I had retail close to the dock.
But, with the Welcome Amiibo update, Tom will buy your current town and pay more depending on how far you have gone with the town, there is a lot that determines that, you could probably find out more by searching.
I also have found sites in the past when I did sell my town last fall after the update that explains the options he gives you when you sell your town, for example he gives you the choice of giving you one lump sum of bells or giving you daily deposits of bells into your bank, which in the end gives you more bells than if you were to choose one lump sum.
Because he will now buy your old town, I did not worry as much where my Retail was. What was important to me was having Town Hall and Retail close to my character's home. I like having my home near the dock. I also had plenty of space in that area to include the Cafe, Police Station and camp site all close to my home. All of that separated by the river with the rest of the town map. The Plaza was separate in the larger area on the other side of the river from my home and the other buildings I mentioned.
One thing to remember, which I think is so awesome, is that you retain your catalog inventory and all unlocked PWPs from the town you are going to sell to Tom.
To me it makes it a little more tempting to start over if you are not happy with your town.
Please excuse being like Blathers and replying with a long post.