From just a technical point of view 3D is better in terms of memory, asset creation, animation, supporting high resolution screens, leveraging the hardware, skinning, and damage states, to name just a few off the top of my head. The choice isn't just for 'marketing reasons'. Slitherine will never tell you why playing a board game in 3D is fun, because it isn't and we all know that. Both companies do of course do tons of market research, but both focus their public message on why their decisions are going to create the funnest / best products. Blizzard entertainment or Apple would never say 'Yeah, we know this product won't please our current fans and isn't really all that great, but marketing said its a good idea!'. That overt emphasis on marketing actually sets Slitherine apart from other studios.
They aren't going to, because they insist on making another Panzer General 3D for marketing reasons, but that's a choice. The devs could relent and model the units from the side as they did in PzC while still using their Unreal assets. They're well past the point-of-no-return so it's best to focus on helping them make it work.
