A: For absolute reliability it is better to pull the slide back. You get a little bit more spring tension and consequently a bit more force driving the cartridge into battery. I had two different situations which tended to illustrate this. One was when the seating die on my reloading press slipped a bit and a batch of ammo came out too long. Occasionally, I would get failures to feed when dropping the slide with the slide release, but pulling the slide would get them to chamber. Another case was when the lips of a particular magazine got slightly bent out. I don't know how or why that happened but that magazine would not load the gun by dropping the slide with the slide release. When I pulled the slide back, this mag would chamber the rounds. So, little variables like that can effect feed reliability and pulling the slide seems to be more reliable than using the slide release.