Then the answer is a dump truck. You're busy. Here's an example.
You need 2 yards of mulch. Get in the dump, go get it. Push it into wheelbarrows from the dump bed while it's tilted up. Sweep up and get paid. Go home.
Drive to trailer. Hook up. Maneuver to yard for mulch. Go to job, dump it on the ground or shovel it out. Sweep up and go drop off the trailer but some idiot parked a mile off the curb and you take 10 mins to back it in.
I'm also assuming you have a trailer full of equipment like every other landscaper, which you can tow with the dump truck. If you get the dump trailer you're loading all that stuff in the pickup bed or piling it in and out of the trailer every time you load, unload, and park it for the weekend. Not ideal and a total waste of time. Time is money.