Is Norton really that horrible?

Okay, a few days back I installed Norton 360 onto my pc. I noticed my computer slowing down and it doesn't run as well as before. I used to use McAfee, but it didn't help against viruses AT ALL. I have Norton now and it's practically the same. I read some reports and people either said it was horrible or great. I have a Lenovo laptop that is only a few years old and it usually runs pretty fast but ever since I got Norton I've had to restart Firefox a hundred times a day because it keeps crashing. Has anyone else used Norton before? Can you give me some advice? Would it be better to uninstall it and find something better or should I just keep it?