As already said the original magnesium arm is a really fine all-purpose tonearm, BUT a heavy SPU or a stonebody Koetsu only really sings in a heavy arm (for example a Glanz MH 94s or FR 64s).
Much better.
Joking aside; The Glanz has a highly effective inner damping, so heavy, low compliance cartridges like SPUs or EMTs that send a lot of vibrational energy into the arm are handled with ease. The Technics arm is „softer“.
But the Technics arm is a very fine tonearm and serves me very...
I ordered a Technics base which was prepared for the Glanz by the dealer (actually the work was done by Clearaudio).
Later I saw there would be a cheaper option by: https://www.acoustand.co.uk/collections/all/products/acoustand-replacement-tonearm-base-panel-for-technics-sp-10r
The Glanz was the same MH-94s on both turntables, the SPU is one of my collection of 7 SPUs, but the differences were comstant. Just more of everything, especially more musical involvement.
After all the 1200G is a mighty fine turntable and with the Glanz tonearm (and an SPU) even better, but if...
Been there done it. And yes it was a lot better than the standard tonearm, BUT the upgrade to an SL-1000r changed things considerably!
The SL-1000r is massively better than the 1200G (even with the Technics tonearm of the SL-1000r).
IMHO the 1200G was only slightly ahead of my old trusty 1210 MkII
Inspired by KAB
http://www.kabusa.com/frameset.htm?/
and Thakker
https://www.thakker.eu/tonabnehmer/ortofon-concorde-r-40-moving-magnet-hifi-tonabnehmer/a-10569/
And now it‘s a serious cartridge :)