I tend to agree with the above. The Umfaan is your basic 'credit card knife,' that is one that will not protrude beyond the boundaries of a credit card if laid upon it. As such, it makes a good keychain or watch pocket knife.
However, the small Seb is a lot easier to cut things with, not only because of the larger scales; the larger blade helps also.
I have found the small Seb to be very airport friendly; they didn't hassle me about it at LAX, where I had left the secure area to use a phone, so had to go back through security. I had my carry on bag with me, of course, and it had a number of wires in it (the charger for my cell phone and digital camera, headphones and small tape player for my son, etc.). When I reached security, they x-rayed my bag, and then politely sent me over to a sniffer machine, and checked the bag for explosives!! I was surprised, as they hadn't even looked in the bag when I boarded in Phoenix. Incidentally, my custom Ernie Emerson CQC6 is also airport friendly; I usually even forget that it is there, so it usually gets left in my leather bag. It was there at LAX also, and didn't even get looked at.
Of course, YMMV...
Walt