Looks interesting. It shares the same case as their 150ah battery. I don't think they are using different technology so they must have found a better way to compress the components like the wiring, cells and BMS board. Hopefully heat dissipation won't be affected.
If memory serves Victron has a proprietary BMS system that can control multiple batteries to work together. Something most drop ins don't so if you go that route you may want to invest in complete system, solar charger, inverter charger, color control panel etc. to optimize the performance and convenience of use.
Yes they are pricey but you will have a very nice system. Our battery bank resides in the compartment where the generator would have been had we ordered it. That was large enough for 600ah bank of (24) 3.2v/100ah cells.