Duty cycle is part of the equation. Bigger pins, heavier pin bosses, beefier frames, more hydraulics, larger lines, better filtration capacity, more oil capacity, more cooling, etc. When they design a backhoe attachment for a farm tractor, it is designed with a particular duty cycle and they actually design them with a duty lifetime in hours. You will not find that data anywhere, but it is part of the design parameters. Whereas a TLB might be designed for triple the duty.
For the average user, the Kioti/Mahindra/LS, etc., will dig all the holes you need and you won't wear it out. But if you plan to run a lot of 8 hour days digging at or near maximum, the dedicated TLB will outlast the farm tractor/backhoe attachment by a long ways.
We sell a ton of tractors, and about every 4th one goes out with a backhoe attachment. I like them, I sell them and folks are happy. But if a guy says he is going to dig septic tanks and do backfills commercially with multiple operators on a daily basis, I suggest he pays the $100k plus for a dedicated JD310 or Cat 416. Or that he gets an excavator.
Keep in mind the quality of the controls. The controls themselves, just the valve bank, on a full size excavator costs more than an entire backhoe attachment for a 40 HP tractor. Yes they are smooth...they should be.
For the average homeowner or hobby farm, a backhoe attachment does a wonderful job. Throw away the shovel! Toss the wheel barrow. Save your back. It's all good.