Which is better? I shoot mainly portraits and wedding.
Any help would be awesome.
I wouldn't be satisfied to shoot a wedding with a 28-75mm on a crop body...I like having a wider angle available. After all, you can always crop an image if needed, but you can't really add what's not there.
I went through this same thing and ended up buying the Tamron 17-50 f2.8. My biggest worry was doing a wedding with a big dress/train that you might need the wider end to get it all. Not to mention fitting many people into a frame while being relatively close to them. If I was only doing portraits I'd go for the 28-75 but think that 28 might not be wide enough for a lot of wedding shots on a crop body.
Ideally it would be nice at a wedding to have 2 bodies with the 17-50 on one and something like a Tamron 90mm / Nikon 85mm or some other longer prime attached on the second body.