As it turns out… Unreal Engines default rendering setting is to use deferred rendering, which isnt used in unity3d as default (they use forward rendering)…
So… by switching from deferreed to forwards I managed to gain a solid 90FPS+ using a 9M poly CAD model…
For anyone else that might experienced this problem and hasnt switched to forward rendering… here is some additional instructions:
https://docs.unrealengine.com/latest/INT/Engine/Performance/ForwardRenderer/#performanceandfeatures