Mark Bales is correct. Weekly maintenance accounts provide good regular steady income, often year-round. Where design/build is very season in most parts of the country and can also go up and down depending on the economy.
I prefer the landscape design/build part of the company. That's the part I work most in. I have other people that predominately manage all the sales, employees, etc. for the maintenance division. But maintenance provides a good, regular, dependable income 12 months out of the year for us. We handle about 270 accounts each week at an average of $165-$175 each. Do the math on that. That's the amount we make each month, 12 months of the year, from our maintenance division.
The profit margin is much better in hardscapes & design/build side of the business. But that side isn't steady.
Not to say it can't be done. Obviously several people have already replied that they don't do much or any maintenance. I just think it's more difficult this way because you don't have a cushion. Maintenance makes for steady cash flow.