ER & Grey's Anatomy

I have to do a school project in which I have to compare two tv series. I've chosen for ER & Grey's Anatomy. I'm very obsessed with Grey's, but not that hard with ER. So, now I'm looking for similarities between this two shows, and I hoped you people could help me :$ So, I wanna ask you all, if you know things that might help me, to comment (A)
Thanks in advance ^^