Hhhmmmmmm. Need to be a little careful here methinks. EAC doesn't actually do the compression itself. It palms that off to flac.exe. I would hope that dbpoweramp does the same...so both should take the about same time for the actual compression.
What EAC does do is copy the CD into a number of .wav files. To do this it does a number of things where speed is somewhat beyond its control eg looking up the Accurip database online.
So, assuming all is equal, it should all boil down to producing the bit perfect .wav file which separates dbpoweramp and EAC. It is possible that dbpoweramp has a more effect algorithm for doing this. It may be that the two apps have been configured slightly differently by yourself, meaning that dbpoweramp is being less rigourous with its copying. Or it may be that dbpoweramp is taking shortcuts.
I have used dbpoweramp for a number of tasks in the past. But, I have to confess, that I have only used EAC for ripping so cannot comment on the quality of the dbpoweramp rips. One thing you could try is ripping the same CD twice using EAC and dbpoweramp. If the resulting files are identical....it would seem to suggest the dbpoweramp has the more effective algorithm.