The guy at the bait shop said don't use mesh sacs as salmon don't like them??
There may be a little bit of truth to this statement but it's mostly an exaggeration as lots of fishermen use sacs successfully all the time. There's the argument that loose roe gives a more natural presentation and/or milks better etc and I wont argue with that. However I would counter that the advantages of using sacs easily makes up for any shortcoming.
it lasts longer on the hook. You cant catch fish if your line's not in the water and by using sacs my line is in the water more often simply because I'm not re-baiting every 5 casts. Nothing worse than putting on a beautiful, juicy piece of roe just to watch it fly off on the first cast

. Cast as hard as you want with a sac and it'll stay put. Float went down and you set the hook but missed the fish? With loose roe you'll probably be re-baiting, with sacs just reel in and cast again.
Which means it's more economical. A jar of sacs (one skein or less) is enough for a days fishing. I dislike prepping roe so anything to reduce that time spent is a bonus in my book. Its also easier on the wallet for those that prefer to buy roe instead of curing their own.
It's less messy. Those guys where literally every piece of gear they own is stained pink are inviariably loose roe fishermen. And I mean everything. Waders, cork, reels, jackets, vest, fingers, you name it. Not that I'm criticizing them, if that doesnt bother you then great, but the thought of all my nice stuff perma-stained pink, red, and orange. no thanks
Plus you can also make use of single eggs so as not to waste any roe. I actually prefer to cure roe as singles as I find it's an easier and more consistent cure method but then you are committed to using sacs.
For roe I use sacs almost exclusively, so I am obviously biased, but IMHO you can rest assured that you are not handicapping yourself by not using loose roe. If anything I would argue that new roe fishermen are perfect candidates for using sacs so that they can spend more time drifting instead of re-baiting...