I use modo for arch viz a fair amount, and have experimented with Unity, and am currently beta testing Lumen RT 2015 (pretty slick tool for that use) and for me, having learned C4D, 3DS & Maya, modo was the best fit.
OBJ out of ArchiCad into modo, easy work resurfacing as all the polygon material tags come through, all the original ArchiCad materials come through - you only need to edit the ones you feel are inadequate for the given render.
modo is a powerful and intuitive modeling environment, and with the addition of the mArch tools has some architecture-specific workflows which work smoothly and well. There was a plugin for modo 701 & 801 called mesh fusion which I used a fair amount which they've now simply included in modo 901, which gives powerful and flexible booleans whilst keeping good sub-division surfaces, - a very nice trick I have to say. With 901 now having both PBR and the original award-winning modo renderer, there's very little I can't tackle with the toolset.
If this doesn't help or you need more details, PM me or we can email.