In my opinion, the weapon pick up sprites in Project Brutality look a lot better than most pickup sprites, they could be possibly compared to Build engine based pickup sprites. Balance is also subjected to change, as that mod is still a WIP. The voxels in PB are actually not voxels, but rather polymesh models that are converted to md3 format, as models are more optimized compared to true voxels. These "voxels" can be toggled with a key or in the settings. I won't explain it any further, as I don't want to bring any form of cross mod drama here.
Edit: Some of the decoration sprites are also subjected to change, along with the effects, as most of the Decorations and effects are borrowed from Brutal Doom. Project Brutality is slowly separating itself from BD, while still use portions of it as a base. Also, voxels are supported by the GZDoom engine, not the mod. Unfortunately though true voxels are horribly unoptimized, even having three or more voxels can slow the engine to a crawl, making it borderline unplayable. Voxels that are converted to md3 are way more optimized and less taxing to the engine. Brutal Doom v21's tanks are also low poly md3 models, and I'm sure other mods also use models instead of true voxels.