Been in both.
Corsa is absolutely the worst 'new' car ive ever been in. I went with a mate to buy it and he also took me in it to buy my rs2k. Loud and boomy inside I was virtually deaf when I got out. Seats were solid and uncomfortable. Shit itself in the corners and this was the racing vxr, 236bhp or so it was claimed. Never pulled away through the a roads in fact I was all over it. Terrible car.
Astra was better but that said I know a few people with them and all had gbox issues. My mates a massive Vauxhall fan and he even said a focus rs all day