I'll take a shot at the question, if you like. (Yes, that's a pun!) Trigger pull on a Glock is cumulative. It is an accumulation of opposing forces between the: trigger, striker, and recoil springs. This interaction of opposing force occurs as the, 'bird's head', located on the rear of the trigger bar, slides down the connector angle. The gentler that angle, the less overall resistance is encountered and the easier the trigger will pull.
No one component in the trigger linkage accounts for all of the pull weight. What needs to be understood is that this cumulative trigger pull begins with the weight of the recoil spring, and proceeds to the trigger bar/connector angle junction. Here is where the trigger spring comes in. It's the trigger spring that pulls against the combined force of the other springs: Namely the striker and recoil springs which it, more or less, sits in between.
It may seem paradoxical, but the heavier the weight of the trigger spring then the easier the trigger is going to be to pull. Numerous Glock Armorers have mentioned to me that an owner/tinker has to be careful not to upset the (gross) balance that exists between these four components. The recoil spring can't be too strong; neither can the trigger spring; and the striker spring can't be too light, either.
I don't build or use Glock, 'range guns'. All of my Glocks are serious weapons that are intended for everyday carry and street use. Consequently, I do not use 4# striker springs. True, 4# striker springs make for a much softer trigger pull; but the downside is reduced primer impact and increased likelihood of an accidental discharge whenever the pistol is roughly handled.
Normally, I won't go either higher or lower by more than 2 - 4#'s on a recoil spring (1 to 2#'s higher is what I, sometimes, work with). Whenever I do go higher I'll, also, increase the weight of the trigger AND strikers springs, too. I run three Glock pistols. All of them are fitted with Lone Wolf's incredibly springy 4.5# connectors, and Wolff Gunsprings 6# trigger and striker springs. My cumulative trigger pull weights occur in a range between 4.9 and 5.2#'s.
Just so you know: '3.5#' is an advertising misnomer. Glock, GmbH does NOT produce 3.5# connectors; instead what the factory actually produces for, '-' connectors are all 4.5#'s; and THESE are what all of the aftermarket Glock parts companies sell. Your combined trigger pull is NOT going to be, about, 4.5#'s. Without the addition of a 6# trigger spring (and, perhaps, a decent action polish job) your cumulative pull weight is, most likely, going to be more like 5.5#'s.
Well I said I'd tell you how the ghost 3.5lb trigger connector worked for me. After installing it I ran 200 rds through my model 22 40 cal Glock @ 20 yds. Trigger pull was noticably less. I don't have a gauge but would guess about 4.5 or 5 lbs. Trigger was also very crisp as advertised on package. It improved my shooting a little but I think it will help a lot more as I get used to new trigger feel. Always have a competent gunsmith or glock armorer work on your pistol. That being said I just found this video on YouTube and thought you might find it's information useful.http://www.youtube.com/watch?v=RaZTch_BVvc