I've been down this route... I had a lot of fun modifying a 1200MK2 but there's no contest, the 1200G is an altogether more refined and musical beast.
I bought a 1200MKII about 2 years ago just out of sheer curiosity having lived with belt drives all of my adult life - LP12, Origin Live, Well Tempered. I really wasn't expecting much from a stock 1200MKII but it didn't take long to realise that there were things this deck did that no belt drive I'd ever heard had ever achieved, so I set about modifying it over the next year and my Well Tempered Versalex was sold on because by the time I'd re-wired the arm on the Technics (overall the biggest difference of any of the mods I did), the Versalex was no longer any competition. In total I performed these mods on the SL1200MKII:
Externalised the power supply, beefed it up following the threads elsewhere on here and replaced the stock motor regulator for an SPower regulator.
Stock platter bearing replaced with a Timestep bearing
Stock rubber platter mat replaced with Funk Achromat
Platter damping removed and replaced with Dynamat
Complete arm rewire from the end of the tube to the RCA connectors from KABUSA along with arm tube dampening
Funk BOING feet fitted
Strobe and speed control removed from circuit
It was all great fun to do and every change was worthwhile. If I was to put them in order of bang for buck then I would say: Arm rewire, PSU mods, platter damping, Achromat, BOING feet, strobe and speed control mods and lastly the bearing which I found to be marginal if I'm honest.
But then I got the itch having read some rave reviews about the 1200G. I was obviously totally invested in Technics and direct drive so I decided it was time to jump in fully. This was back in January 2020 but even back then, the Richer Sounds price had just jumped up to over £3K but I managed to get one from Doug Brady in Warrington for £2600 (I know that this was still the price about 6 months ago, so worth checking with them).
Although I was really enjoying listening to vinyl with the 1200MKII, it didn't take more than a few minutes of listening to the 1200G to realise what was missing with even the modified 1200MKII. There is still a certain 'greyness' (that's the only word I can use to describe it) about the sound of the MKII. It lacks the colour and the sheer scale you get from the 1200G. It follows that if you like the 1200 then you will definitely love the 1200G, but what the 1200G brings most of is finesse. The 1200 always feels like something of a workhorse - A solid and dependable one, the 1200G is just so much more refined and you really do feel like you're extracting everything out of each record you play without limitation or colouration. The guys I chatted to at Doug Brady told me that the 1200G is 90% of the way in terms of sound to a 1000R. This article also went a long way towards convincing me:
https://criterionaudio.com/2019/05/2...rntable-shoot/
To me, and as someone who has been through a fair few turntables, I feel like the 1200G is everything I ever wanted from a good deck. It's an absolute joy to use, there's no faff, no constantly having to tweak about with it. It's pretty much set and forget. It could well be my last turntable.