Yes, the extended part of the trigger must be depressed before the overall trigger can be pulled. This is one of three safeties on the gun: 1) The trigger safety, which keeps it from going off if it snags on a holster or similar, 2) there is a firing pin safety (internal) that blocks the firing pin from protuding through the bolt face unless the trigger is pulled to the rear, and 3) a drop-safety (internal) which prevents the firing pin from being pulled back and released unless the trigger is pulled to the rear.
In response to posts related to the glock being unsafe or going off when dropped... I'm not being an e-dick, but any story about a glock going off from being dropped is very hard to believe. From an engineering perspective, it isn't possible unless the gun was tampered with or was incredibly poorly maintained. Unless you manage to drop the gun so that the trigger is actually pulled cleanly (and jarring it won't do shit due to the trigger safety). Note that any gun that is tampered with or woefully (and I mean horribly) maintained can have its safety measures compromised - a glock is less likely than most guns (including the other two you posted) to suffer failures of this type, IMO.
Most of this info except for the last opinion can be verified on wiki or any number of other sources. The glock is a safe gun, equally or more safe than any double-action gun or literally all revolvers. It is used by many (many many) law enforcement agencies around the world - many of which put their guns through tests - and to my knowledge NOT ONE has ever caused a glock to fire from a drop.
To the original poster: shoot all three guns and buy the one that feels the best to you. If you can't find a place to do so, then get to know your local gun-owners and it will happen - you will know them soon enough if you are practicing often as all owners should...