replacing tonearm question?

@simao 

the photo is of a standard lifter that I have restored (it is not a Sumiko or Jelco that is exactly the same) but they are practically all the same and simple to disassemble.

@best-groove  In much the same way a 1% THD tube amp sounds better than a 0.05% THD solid state amp, the friction measurements are so low as to not matter. What does matter is how it sounds. The Jelco 850 is radically different from the other gimbal bearing models in that it uses a hardened precision knife edge. My Jelco 750 bested the Sumiko and the 850 is far better than the 750.

@noromance 

If what you say is true, then the manufacturers could use stone bearing balls carved by Fred Flinstones himself if friction isn't important.
The friction heavily affects the suspension of the head, the cantilever, the tracking, going to compromise several elements.
Every detail of an arm is important, but the bearings and clutches they possess must be taken seriously.

That is not what I said or implied. Some false equivalence in your example. My argument is that at 25mg, the amount of friction ceases to be a primary concern. Stability and control of resonance is also important. It should also be noted that these Jelco arms are relatively inexpensive so the value-performance ratio is high.

Because the cartridge has rather extreme leverage over the bearings it would take a pretty bad bearing to dislocate the cantilever one way or the other but the "noise" from a rough bearing can be transferred down the arm to the cartridge. Tap lightly on your tonearm tube towards the bearing end. If you can hear it you can also hear your bearings if they are not absolutely smooth. 
Another fun experiment to determine how well your turntable is isolated. Keep the turntable off and place the stylus down on a stationary record. Turn the volume up and listen to what you get. It should be dead silent other than the noise from your phono amp. If the cartridge is too stiff for the tonearm it will start feeding back wildly. Too loose and the tonearm will start bouncing. All this just from the energy in the room.