what do you get with an arm upgrade?

just got a new cartridge (urushi), and am wondering what i would get if i upgraded my expressimo arm.

qualitative differences? if it tracks better, if it deals with resonances better, etc, how does this translate into what is heard?
If you are Lee Majors - a bionic arm!
If the arm is truly an upgrade, then you'll get better sound overall, with the appropriate matching cartridge. Exactly how it will sound depends on the table, arm, and cartridge used. Expect less colorations, better detail, possibly better bass or more liquid presentation, more dynamics, more "lifelike" sound......

Could be alot of things. Depends on the combo and the setup.