since I was more used to the square notch rear than the express I found it easier to use the square notch... I also found my consistency was better with a replacement front square bead with undercut front plane from Ken Oneil.
I still have the express and if I was to be using it in a short range shoot fast situation, then I would put it back on, but I just could not get used to the round bead front with either rear; the bead was not crisp looking enough for me to have repeatable results I could have learned it I am sure, but not as fast as I wanted it to happen. MY groups tightened up immediately with square front and rear sights.. but 25 years of those sights on my pistols could have something to do with it.
dk