I'ts hard to say really because neither of them are perfect.
I reacon Wreath is one of Opeth's best tunes, as is By the Pain but the rest of that album, when you get over the initial buzz of it becomes boring because you know exactly what is coming next.
BWP was very exiting at the time of it's release. The Lepar Affinity, Bleak, Harvest and Dirge for November were all favourites at the time. But these days it is slightly hard to listen to for me, because of the same reason.
So Deliverance is the winner for me, simply becuase there are 2 songs on there i still don't begrudge a listen.
In My opinion the first 4 albums are by far the best and opeth will probably never top them.