same engine so therefore same skins really. but i do also agree that the hossies look a tad under detail...then again they released cs:s pretty much unfinished, so i guess hl2's models will be more detailed
I would imagine the normal everyday resistance fighters will probably look like the CS:S hostages... main characters or important characters in hl2 will have higher poly counts and look better (alyx, barney, gman, etc etc)