Right in terms of geometry lets look at the 17.7 inch YT vs the 18 inch Cube.
* Wheelbase: The Cube has a longer wheelbase. This will be more suited to high speed runs than the YT. The YT will be slightly better in twisty terrain.
* Chainstay length: The Cube has a longer chainstay length. It will be more stable but less easy to manual and a little more difficult to jump with.
* The cockpit: The cube seems shorter, it will have a more upright position – it might help with lifting the front up I guess.
* Wheel size: The 650b wheels on the Cube should theoretically roll better and add stability but may be a little harder to jump.
Conclusion – The Cube will be a bit better for steep fast high speed runs whilst the YT will be a bit more playful in tight trails and jumps. However the 1KG weight difference should go a long way in making the Cube more poppy/playful off jumps than it normally would be.
That would be my analysis if I were trying to decide between the two bikes without riding them. I’d definitely go for the Cube – because of it’s light weight coupled with it’s long and low stability inducing geometry.
The sizing on the YT’s is weird as well, the next size up… the large has an 18.89 inch seatube. It’s wheelbase is a little longer than the 20 inch Cube – so this analysis doesn’t really play out for the larger model.
If I had the choice between the 18.7 YT and the 20 inch Cube – I’d go with the YT for the longer front end and shorter chainstay. I wouldn’t buy it with BOS forks in a million years though.