In answer to your question, I run Kaspersky 5 for resident protection. I use Avast once or twice a week as a failsafe. In that running two resident antivirus programs can cause problems, why should I not do this? Are there any independent lab results stating that Avast is better than Kaspersky?
Whilst there may not be a definitive answer to which is better, the two AVs offer different levels of protection - avast offers protection for p2p, IM, email, web shield (http) and standard shield (on-access). So I would chose the one that offers most of the functions that I need and use the other as the secondary.
An easy way to disable providers, rather than have to delete files is open the Resident Scanners window (left click the avast icon) and terminate those that you don't want active. Or use the Add Remove programs, avast! Anti-Virus, Change/Remove button and scroll down to Change, click next and follow, untick the providers you don't require. You may need to be on-line to do this.