the difference is what you want the adhesive to do,...
I want the bond to survive a hard thrashing, banging superglue is how you break that bond, it isn't flexible in the slightest. Say you were making a rubber band powered glider, parts of it are superglued (those are intended to break away on impact ~ like each of the wings from the fuselage) and parts of it are assembled with 2 part epoxy (available at any hardware store, you mix it on a paper plate, a couple of minutes to turn milky colored with a toothpick or stick from the yard). These are pieces that are intended to survive an impact without separation,... epoxy has a little flexibility. Say the rudder and tail section, they probably wouldn't be the first point of impact from powered flight ending anyway. <LOL>
Cleaning out the release agent and roughing up the edge of the ferrule may seem like overkill, but it's not that tough to do it perfect. You need an emory board for finger nails (or some other gentle abrasive), a paper towel and skinny insertion device (like a coat hanger) heck even an ear cleaning swab with alcohol on it, or windex will work. You don't want to adhere to the releasing agent (used to get the stick off of the mandrel when it was made!)
Building up the stopper thickness with electrical tape makes a nice clean bonded edge (also prevents over insertion), as it just removes the excess epoxy overflow as unwrapping takes place. Wait for it to dry first!!!
I carry a repair kit, you can bet both kinds of adhesive are in there too. But if I can wait until I get off of the beach I can do it right!
Placing the ferrules into the outside pieces of the leading edge assembly just seems like a no-brainer to me. No "both ends sealed with solid ferrules", also the kite "breaks down shorter" (my A-bag is an oversized fishing rod case from Orvis). Lastly, on a personal level, I run a different bridle from most folks so my kites bend on the other 3rds instead of in the middle, therefore I also prefer a varying degree of flex in the LE. That is accomplished by use of a travel frame layout with stiffer members in position two and five from the other 4 spots along a six piece leading edge. Usually green race (2) and diamonds (4). for convenience these tubes are taped together in pairs making a three piece LE. I want more stiffness at the intersection of the down spars and LE. Having the ferrules on the outside 2 LE pieces makes changing the flex easier for me on site.
I will grant that I do almost nothing as others do, I've spent lots of time experimenting and testing for my own preferences,... over decades in fact. The great thing about kiting is .... "you take the best and dump the rest!" As you'll hear hundreds of ways to get to your promised land.