Hi @Darya_Berezniak -
Just so you know it’s not just @lassoan, I would also encourage you to try building your app on Slicer if at all possible. Not just because it’s better for all the reasons he mentioned, you also avoid black box commercial software and license fees.
As you can see if you look at the history of VTK, such open community projects often outlive and outperform the commercial competitors.
Of course Unity has some slick interfaces - send a link if you have any cool demos to inspire (and humble) the SlicerVR team.
-Steve