What benefits to expect from tonearm upgrade

in my experience a change of cartridge to a better one, brings greater rewards than a change of arms.

This is not correct. I owned a high end store before digital and have owned, sold, set up a huge array of TT's and arms including Sota, Linn, Pink Triangle, Townsend, Goldmund, Roksan, Technics SP10's, Kenwood L07D's, Verdier, SME, Well Tempered, Garrard 301/401, Thorens 124/5/6 and many others. Arms including Linn Ittok/Ekos, Syrinx PU2/3, Zeta, Alphason Xenon/HRS, ET1/2, Well Tempered, SME 3009/3012/iV/V, Odyssey, Hadcock, Naim Aro, Dynavector 501/505, Goldmund T4/5, and many others.

Putting an expensive cartridge on an inexpensive arm is like putting Formula 1 or Indy racing tyres on a family sedan - the handling does not improve, in fact you will go round corners much slower because the car was never designed for these tyres.

Let me give you another example.
Assume I have a Rega RB301 with Exact MM cartridge.
If I put a Koetsu Black or Lyra Helikon on the Rega arm you will hear a significant difference. It may even track ok. An experienced ear will also hear fragility, lack of coherency due to the mismatch.
If I put the Rega Exact MM on a top of the line tonearm it will track better, and you will hear a more stable and coherent sound than the Koetsu/Lyra in the cheaper arm.

Another point to consider - MC's can put a lot of energy into the arm. If you put a low compliance MC into an inexpensive arm you are most likely to wear the arm bearings out in a short space of time.

Kiddman was absolutely correct when he said -

04-09-14: Kiddman
Without the right tonearm you will never realize the potential of your cartridge or turntable. Unless both are very subpar, get the great tonearm first.

Jperry, it not clear ,to me at least, which arm you liked better.

Schubert, when I reread my post I can see it may not have been clear. The Basis Vector tonearm was far superior to the Basis modified Rega tonearm. The difference was to me astonishing because I did not think changing just the tonearm could make such a noticeable difference. This was in my system using the same turntable and cartridge. Kurt_tank earlier in this post indicates he had a similar experience.

Dover...you didn't read my post carefully. I agree with you if you go from a crappy arm to a great arm....however...if you listen to arms of the same relative class, any difference is minimal.

Very helpful Jperry, thanks.