I have very limited experience with inflatable kayaks, but I think a strong case can be made for an Alpacka over other craft if you want something that will roll up small.
A packraft will definitely be the best as far as weight and bulk. I think most inflatable kayaks are several times the weight, and presumably compare similarly in bulk. So if you’re going to be carrying the boat (ie “packing”) then the packraft is very nice.
In flat water, you’ll find the packraft both slower and less graceful than a hard-sided kayak. Max practical speed is 2 - 2.5 mph, as opposed to 4+ for a sea kayak. I’m not sure how it will compare to an inflatable kayak… I’ve heard some who think they aren’t much faster than a packraft, but maybe their inflatable sucked or was improperly used. So if you’re going to be spending a lot of time in the ocean and are doing trips where driving to your put-in works well, then the hard-sided kayak will perform much better.
That said, packrafts are quite capable in the ocean, and open up some interesting routes. When we came through Vancouver in summer 2007 we walked north through Cloverdale to the Fraser, floated down to where the river splits apart in the delta, walked across Vancouver and over the Lions Gate Bridge, then hiked along the Howe-Sound crest trail until we ran into problematic snow. From there we dropped down into the Vancouver city watershed where we were kicked out by a security guard and walked down to Britania Beach, crossed Howe Sound and hiked logging roads and bushwhacked to Red Tusk Creek and down to paddle Salmon Inlet… it continued like that all the way through the inside passage, through southcentral Alaska, and to the first Aleutian Island.
In the ocean, Alpacka packrafts are stable in rough water, easy to put in and take out, and easy to re-enter if you’re flipped. And they’re really in their element in rivers.