get the biggest trailer you can accomodate, parking, streets, towing cap of your vehicle, financially, etc. If you plan on staying in the business, there are going to be times when you'll need a big trailer.
When i started out i had some 4x8 utility trailer i draggeed my 50" around with. i bought a 6x10 thinking it would be more than large enough, now i'm thinking about buying a Z, and my 6x10 ain't gonna be long enough for both my WB and my Z. My next trailer will probably be a 6.5-7x14-16 footer.
Efficiency = Profit