Based on your questions about the Mammotion Yuka Mini and Yuka models:

Moving Between Lawns

While the Yuka Mini is designed to navigate between different lawn zones automatically, your specific situation (thick gravel and a locked gate) presents challenges. Ideally, you would create a navigable path between your front and back lawns for the mower to travel autonomously.

Recommended approach:

If possible, create a smooth pathway through the gravel area that the mower can traverse
Consider installing a gate or passage that the mower can navigate through
If creating such a path isn't feasible, physically carrying the Yuka Mini (16.5 kg/36.4 lbs) between zones remains an option

The mower is designed to handle multiple zones without manual carrying, but your specific obstacles may require some modification if possible.

Depending on the depth and type of gravel, you want to consider the Luba Mini AWD as it has 4WD. I will be testing the Luba out crossing a gravel drive in the next couple of weeks. I will update this when I have the results.

Yuka Mini vs. Yuka Decision Factors

Yuka Mini advantages:

More portable if you must carry it
Lower cost entry point
Adequate for your 550m² total lawn area (handles up to 800m²)

Yuka (standard) advantages:

Stronger cutting power
Better handling of complex terrain
Potentially cleaner cutting pattern

Resale Market
There is a developing second-hand market for robotic mowers, though Mammotion is a relatively newer brand compared to established names like Husqvarna or Worx. If well-maintained, you should be able to recoup some of your investment if you decide to upgrade later.

Regarding Stripes
The Yuka Mini does not create prominent lawn stripes like a roller-equipped traditional mower. If visible striping is important to you, the standard Yuka may provide slightly better results due to its heavier weight. more powerful cutting system, but neither is specifically designed for creating pronounced stripes.

Given your lawn size, the Yuka Mini should be sufficient unless you have particularly challenging terrain or strongly desire the additional features of the standard Yuka.

Thanks
Mark