The YUKA Mini would be a great choice for your 300m² garden due to being more advanced in its product cycle compared to the others you mentioned, therefore has more functionality at this stage. While all three options (ANTHBOT Gennie 600, MOVA 600, and MAMMOTION YUKA Mini 500) are designed for smaller lawns like yours, the YUKA Mini offers more refined features and capabilities that make it stand out. One significant advantage is that the ANTHBOT Gennie 600 does not have 4G capability and therefore you would need good Wi-Fi signal across your lawn, which could be problematic depending on your property's Wi-Fi coverage.

Another important consideration is that the YUKA Mini also has the option for iNavi and therefore eliminates the need for the RTK station for good GPS signal. This makes setup and maintenance simpler, especially for a first-time robot mower owner. The split garden layout with just one tree should be easily manageable for the YUKA Mini, as its navigation system is well-equipped to handle such obstacles and separate zones. Its more mature development cycle means you'll likely encounter fewer software issues and benefit from a more polished user experience compared to the alternatives you're considering.

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https://easylawnmowing.co.uk/mammotion-yuka-mini-review/

Hope this helps
Mark