(You need to Login or Register to view media files and links)above is a rather lengthy discussion on the same topic
Myself, I don't have any traditional canvas canoe packs - I 've never liked that design for several reasons - mainly because they don't come with hipbelts or padded shoulder straps, and are way too big, which means they will be way too heavy when fully loaded. Many of the more modern "takeoffs" of the design do have good straps and hipbelts - but they are quite expensive and big. Too big for my taste - I don't like having my packs stick up above the gunnel line - the envelope style canoe pack seems to be designed to sit upright in the canoe, two side by side - too big a wind catcher (look at a Piragis catalog and you'll see pictures that show that - not my style, though I commonly see this in Quetico). I can normally lay my SST pack down flat in the bottom of the boat, On the other hand, there are a lot of pvc drybags that don't have hipbelts either, so I have the same issue with them - unless very lightly loaded, they don't carry comfortably at all - fine for riverside camping, but not for real portageing.
I think its more of a background thing - if you have a background in river tripping, you will likely have used the pvc drybags - if your background is learning from someone who has tripped with the traditional "canoe pack" design, you'll probably favor that. Location matters too - while the "canoe pack" is commonly available in the Ely area, they are not common elsewhere - it has been the river runner's drybags that are commonly available - the internet has chnaged that, but still, if ou go into most outdoors stores, you will find pvc and not canvas.
as far as ol Cliffbar goes, I don't know the man, but my guess is he'll endorse anything you pay him to endorse, and his opinion is just that - worth considering, but I make up my own mind about what I like. Would a pvc pack hold up as long as a heavyduty canvas pack IF you drag it across lots of sharp granite - I doubt it, but I"m not gonna drag any pack like that, so that doesn't matter much to me. I've never read any of Cliff's books - never felt the need - I like to figure out things for myself - I'm pretty good at it, actually.
to me, its whatever works for me (or for you) - there is no one best answer. When I go solo, my main "canoe pack" is a cheapo 12 oz, medium sized nylon duffle bag from Campmor that I toss atop my G-pack - works for me.