Basically the exact same thing. Some of the small differences are:
- different lining design (pattern and color)
- different hardware color on some pieces (silver or grayish instead of black)
- no stampable name tag on Gen 4
- decorative leather strip on Gen4 (looks really upscale and better than Alpha)
- some rare pieces have a slightly different interior layout (pen loops not in the same place)

That's about all that I could think of. THey even kept the model numbers the same mostly.

What I am not sure of is if Gen4 is the same as Gen 4.4 and people just omit the .4.

Till