TLBs may do a better job digging but usually because they mount larger backhoes not for any other reason. The trade off is that they give up 3pt flexibility (usually) and sometimes PTO power.
The TLBs that use only one seat are better diggers vs an equivalent
weight/size non-integrated tractor/hoe is because they have a closer-
coupled hoe to the center-of-gravity of the tractor. They use a more
substantial mounting frame and attachment, too. Also better departure
angle for ground clearance. Incidentally, the TLBs also have more hyd
flow available to the hoe. Again, I stated that the sizes and weights
matched for comparison purposes.
As for the ergonomics of a single seat, I found it to be of no value on my
B21, since you had to fully dismount the tractor to rotate and move it.
On a Case 580, however, the swivel action is very useful and productive.
The JD 110 flops over, and I gotta wonder how well that works, but I have
no experience there.
True, the 580 has no 3-pt, but the JD110,
B26,
L45, etc, all have 3-pts.