Needs opinion: Garrard 301 with SMG-212 or RMG-309

I purchased a Garrard 301 with a plinth that is installed Ortofon SMG-212 tonearm. I have not purchased an SPU cartridge yet. I also bought an Ortofon RMG-309 arm from buying frenzy. Well, I must have been crazy. Now I am out of $$$.

Keeping both arms is not an option due to financial reason. So, I need to sell either RMG-309 or SMG-212 arm to fund for a new SPU cartridge. Which way would you go?

Is RMG-309 so much better than SMG-212? If I were to keep RMG-309, I need to sell the plinth and SMG-212, and buy a new plinth that works for 12" arm.
Or, the difference would be marginal and it is just better to keep the plinth and SMG-212, and sell RMG-309 to fund for a new SPU cartridge?

Any input would be appreciated. I have BAT vk60/vk30 and Tyler Linbrook signature system speakers. My current two turntables are Thorens TD145 MKii with AT150mlx cartridge, and Clearaudio bluemotion with Ortofon MC20 cartridge. I hope this Garrard 301 with Ortofon arm/SPU cartridge would perform far better than the two tables.
sorry for late response....I have both arms and also Garrard 301 and bunch of SPU cartridges....I would keep the RMG 309 even if you have to do different plinth...the longer arm is definite advantage especially if you will use the SPU cartridges. One of the best set ups are lucky!