I would also prefer Blender instead of Sketchup. Sketchup is only in the base version free. Blender is completely free , but needs more time to learn. It has a hundred more options like Bumpmapping etc.
Most current PC-Building pieces use bumpmapping for more realism. Apart from that you will maybe want do more in 3D later and once you've learned Blender you have all options open. There are tons of OFFICIAL and certified free video tutorials for blender available.
And why should you first create your model first in Sketchup and export it then to Blender. In that case you need to learn two programs instead of one, which is more than enough.
As I've seen the models here I get a little stomach pain . We should really thing, if we want modular sets, like the building pieces, we have currently in PC or the great versatile sets from RCT3 or if we want that cardbord models that we currently see in RCTW or Theme Park Studio (I think, the models above are from that game).
I hope someone at Frontier will give us soon a kind of guide with measuring tools and instructions, how we can import our creations to PC.