The main difference is that the iiWA is a Collaborative robot. Also, the iiWA uses a different OS and programming language than the "mainstream" KUKA robots. The iiWA is more complex, and has 7 axes in the arm rather than 6. The iiWA senses collisions and forces with the whole arm, not just the EOAT -- the iiWA will detect its elbow touching something, and could potentially be programmed to work around it, whereas a "normal" robot would simply torque out.
All other factors being equal, if you don't need the iiWA's unique abilities, you're probably better off using a "normal" robot with an FT Sensor in the EOAT.
Of course, this depends on the application. In certain uses, an iiWA may have a more delicate and sensitive "touch" compared to a normal robot with an FTS. An iiWA is aware of its payload and its relationship to gravity at all times, where an FTS is much "dumber" -- normal practice with an FTS to to line it up just before contact, then tare (zero out) the FTS, so that only contact forces are "visible." For a complex assembly motion, this could become problematic, and the iiWA might do better.
The iiWA is harder to maintain -- basically, anything that goes wrong with it requires it to be shipped back to the factory. It can't be field-maintained or modified the way a normal robot can.
Also, the iiWA is more finicky, and more rare. This makes it harder to use, and harder to find support (formal or informal) for.
how good is the LBR iiwa robot suited for assembly operations?
any robot is only as good as the integrator. keep that in mind when you spend big chunk of money on a robot and try to get integrator that has little or no working knowledge of that robot.
i have seen LBRs used with a very powerful tool, that was capable of generating torque way above the limits of the LBR but... the integrator used clever design with a pin that would rest against the assembled part and take reaction forces that robot on its own would not be able to handle.
I have seen that this robot has no force/torque sensor but it uses the motor currents (for force feedback) to perform assembly operations.
What is the difference between LBR iiwa and and a robot equipped with a force/torque sensor (ATI)
actually that is not true at all.
LBR iiwa not only has the torque sensors but they are on every robot joint. also each of them is redundant, allowing their use in safety applications.
in fact the LBR is not only collaborative, this is by far the most sensitive robot you can find. it is so sensitive that can literally respond to a breath of air. compared to LBR other cobots are quite crude, force needed to make them react is rather substantial, more like pushing table out of way.
common industrial robots do not have any sensors so the only way to perceive external forces is through:
a) motor current (which is very crude)
b) use of external force/torque sensor at the robot flange (sensitive and flexible option).
c) use of external force/torque sensor at the foot of the robot (robot mounted onto sensor). this is crude since weight of the robot itself accounts for huge part of the measurement.
Some collaborative robots (Fanuc) seem use that last approach. It is cheaper and easier to make and maintain since rest of the robot arm is like conventional robot. but sensitivity and accuracy are low.
