It is better to move the file to chest. If you have moved the file to the chest then, u are secure that the malware will not spread
If it is a necessary OS file , you may have to restore it back whereas if u deleted it, u can never even dream of getting it back.
Plus you can hope for some day when Avast will download an update to repair that kind of malware.
And if u feel that the detection is false, u can e-mail the file to avast form chest.
You can do none of the above mentioned tasks if u deleted the file.