converting NURBs to poly can be easy if you already got model that built from NURBs but I could say that it is not a good choice..even you can control poly counts while converting but you cannot control it's shape...for game modeling every polygons have to do their job in good manner, like every face that you inserted should make model to form some different shape...so if you convert it by choosing it to be very smooth, to be as same as the original NURBs...it may takes many polygons in scence which means that more hard job to engine...if you want to control it poly counts, shape that came out(often) won't fit with the thing you wanted..... so maybe starting with poly and ended with poly is the best +_+...I think.......