How important is the tonearm?

It is my firm belief that the arm matters more than the cartridge. I think it is indisputable that a bad arm will negate most if not all the virtues of a cartridge. I have used many, presently have a Graham 2.2 set up and a Jelco 750 awaiting the restoration of a Linn LP 12. As to which arm and what design characteristics should matter there is little agreement. Choice will be governed by the compliance of your cartridge, compatibility with your table, and personal preference. Do not equate price totally with performance, companies like Jelco have economies of scale and give great value for the money. Arms made by them have sold for high prices under famous names in the past and may still for all I know. If you want the most out of your cartridge a good arm is essential; the choice is up to you: air bearing, linear tracking , unipivot, conventional. There are good arms using all these configurations.

Actually, the mass of the arm has very little if any effect on groove wear and designers do not attempt to keep it as low as possible. The mass of todays arms is higher than it was in the 70s in general. Something like the Transcripters VESTIGIAL arm with its mass of 3 grams or less would be laughed at today. The SME 3 arm had a mass of something like 4.5 grams, the 5 is 12 or 13. Low compliance cartridges will not work well in low mass arms in general. The critical factor in groove wear is the shape and polish on the stylus. Long ago there was an experiment in which an LP was played several hundred times tracking at 3.5 grams with a high quality stylus; there was no wear when it was examined under a microscope. Badly polished styluses with irregular shape are the most danger to grooves. I remember it the 70s HIFI News had a cover showing the magnified stylus of a group of top cartridges; many were obviously misshapen. I don't know what todays would look like; better I hope, given current prices.

What's wrong with taps for a dead arm? Sorry, the devil made me do it.