Turns better with the tag up
Similar capacity to a tandem
Load on rear axle is adjustable, which means the load on the front axle is adjustable, especially with sliding the jib on the hoist
Truck is lighter and cheaper with a shorter chassis height
Smaller hoist, I got that hoist new for below dealer cost... it'd be underkill for a true tandem (24klb rated hoist vs a 40k+ rated hoist).
The hoist manufacturer specs a single axle chassis for that 24klb loader, which I think doesn't do the situation justice. The single axle chassis was ~12klb, the hoist is 4klb. Add a container and you might have 10klb of payload meaning doing tree work you'll be constantly practically overloaded (excluding legalities) before you tow a trailer with a decently loaded tongue making for a miserable experience. Add a tag axle and you have better turning radius with the drive axle moved forward, can haul variable loads in the container and on the tongue, have better braking... long story short I'm a big fan of the high lifting tag axle. If I built a tandem hook lift I could easily see me putting a tag on the back of it for the same reasons (with a bigger hoist).
Just watched your video, didn't realize the truck was already built (was skimming this morning knowing I'd come back to the thread). For $10k that's tough to beat. I wouldn't go buck wild with smaller containers that only fit that truck. So far I only have one container for my truck 2 years later. I don't really want to be a container service, there's better money doing tree work/hauling tree debris. If I had employees, that could certainly change. I could also see adding a container for a specific job or circumstance. Being able to put the container on the ground makes it far easier to load the high volume container, especially with big/huge wood, like wood big enough you cut/rotate it so it will fit inside the width of the container kinda huge.