Typically they are different, mulching blades have a larger cutting edge and are typically curved to increase the velocity of the circulation of grass, this in turn can cause greater efficiency when bagging but it will depend on the blade. You will usually see them labeled as "high lift" for bagging

I have regular blades on my Craftsman with a mulch plug, and I can't see much difference except the grind is a not as small. Still works good, but don't cut wet grass with either setup. You'll have a job cleaning that deck.

I just installed the mulch kit on my X300. I didn't notice a difference in the blades. The insert didn't fit the deck at all well. I had to modify it.

I have a Deere LX280 with 48: deck with mulching kit and mulching blades. It definitely works well if you cut very slowly (I cut on max height setting - 3.5"). If you don't cut slowly, it tends to leave uncut strips of grass. Much better results without mulching kit and use of gator blades (regular blades are probably ok but I went straight to the gator blades). Then I cut in a pattern so I keep re-cutting the grass I just cut and eventually work it to the outside of my lot. This gives a great result. I recommend this latter approach.

Tom