Buying a pack with or without compression straps?

I greatly prefer using the pack for compression instead of using compression stuff sacks. I find that that allows for quickly pack loading in the morning.

The Mariposa does have loops along its side that you can use to add compression along the side panels.

I don't have much bear canister experience, but when I carried one, the bear canister was stuffed vertically inside the pack with the rest of my gear around it. Things were so tight that there wasn't much compression left to do.

I like compression straps on a pack so I can keep the load close to my back (and not have to lean so far forward to balance the pack's weight).

Without compression straps, things can tend to collect in a clump at the bottom of the pack, instead of being high and close to my back. Depending on your gear, you can dance with that by using some tricks – on low volume trips or after you've consumed much of your food, you don't pack your puffy layer or sleeping bag/quilt so tightly but leave it fluffed up in the bottom of the pack. Then you load dense items high and/or between bag and the back of the pack so it is wedged in close to your back. Note that you are also trying to keep the smooth, cushioned things against your back, so it takes some practice to get it all dialed in.

Definitely a pack with compression straps to allow you to secure the load as your volume varies. What is better are compression straps that can be removable for even more modularity.

I have a couple of packs. One of the is an Aarn that I wanted to lighten so I removed everything I could including the compression straps. I fill this pack completely and it has an internal frame so I didn't lose much. The volume items taken on my other packs can change so I have left the straps on.