I was curious as to what is better a boot time scan or a regular scan which 1 picks up the virus or trojans if found.
The boot time scanner have full access to all files. The regular scan with the administrator account has enough access rights.
Both can be configurated to scan archives.
So, I will run regular scans (monthly) in one or each way. Not that often, with archive scanning turned on 
They both use the same virus database, so technically it would be the same, however, it also depends on the settings that you use in either scan.
The boot-time scan is normally used if a detection is found in the normal windows mode and avast can’t deal with the problem whilst windows is running, e.g. a file in use by another program, virus in memory, etc.
It is at those times that you would schedule a boot-time scan, it isn’t there as a substitute to the conventional on-demand scans this you run periodically (you decide the duration, etc.).