I found that Antivir gave better protection and slowed the system down less than Avast.
But that was a few years ago now.
My favourite antivirus is AVG 8, but NOD32 is good, just that I don't want to pay and it slowed my system down more than AVG. Kaspersky also does well in tests but for the absolute best protection I'd choose NOD32. AVG for me offers a good compromise, in that it's free, uses evry little resources, and offers very good protection too.
As for antispyware, I wouldn't personally pay for it. Spyware Blaster and Spybot's immunization, plus Spybot's scans and AVG 8's realtime protection, and a dash of common sense seem to work fine for me.
But, if you're happy with the programs you use, keep them, they will also do a good job of protecting your computer from unwanted nasties.