Personally I don't have an Issue with the factory trigger and I figured if you have a Gen 4 block 19 and you can shoot it well with the factory trigger then leave it alone, If it aint broke then don't fix it.
But to answer your question, I have heard the Zev tech triggers are nice as well as the agency arms triggers. If your happy with the trigger pull its self you might consider just upgrading the trigger shoe. (replacing with the flat trigger shoe)
I believe you can get these by themselves from Agency Zev and many others.
If you want the more rounded trigger like from the factory rather than the flat trigger I have heard the lone wolf adjustable trigger is alright. They also sell just the trigger shoe if thats the way you want to go.
I personally have never fired the gun with any of these triggers so my opinion is worthless but I have dry fired an agency arms glock with their trigger on it and the flat trigger face alone is a nice improvement.
I've always used the Ghost Rocket trigger on all the Glocks I've had. I prefer the trigger bar with the overtravel tab. Just spending some time polishing the stock stuff helps also. I should stress though, if you don't %1,000 understand how everything works internally than please take it to a certified Glocksmith. NHT3 is well known on here for his Glock work.
Personally I like Apex stuff the best they are wizards with Striker fired guns. That being said you could just ditch the Glock and get a Sig P320 you do not have to mess with to begin with
Get a G17 smooth trigger, and shoot the pass out of it. Many aftermarket triggers in the Glock have shown to be unreliable to unsafe. You may consider a "-" connector as well.
Another vote for the Ghost Rocket. Just take your time filing the tab till the trigger releases and your golden. May require assembly and disassembly a couple of times but well worth the effort imo.
Are you talking about the overall feel of the trigger in regards to pull weight and crispness or the trigger shoe? I've been wanting to try out the overwatch trigger but can't seem to do it as I carry both my 19's and the factory trigger/bar with a ghost edge connector and 6lb trigger spring is plenty nice for a defensive trigger and keeps it 100% reliable
Glock store double diamond 3.5lb with titanium safety plunger. I leave all springs stock. It makes for a very short take up and a solid wall and a very crisp break. The reset is short also, I've had zero malfunctions with this set up. You can leave your file in the tool box and no need to polish anything with this set up.
I have OC Custom triggers in my Glocks with pre-travel and over-travel adjustment. I supply my own 3.5 OEM connector that has been gone over. Uses all OEM components to include the trigger shoe. The cost doing it this way is well under $100 and I get a nice short smooth trigger with a short positive reset.
For my carry 19 in order of improvement:
Glock 17 trigger shoe bar assembly (smooth) - probably the biggest improvement because the serrated trigger feels uncomfortable to me.
$0.25 trigger polish with a q-tip and metal polish
6lb wolff trigger spring
apex safety plunger
I personally have not found an aftermarket trigger that I thought was a big enough of an improvement over the stock to justify the price honestly. After I get out and shoot them a bit I think they all feel just fine (I'm also very used to it though). I've felt the zevtechs and they are nice, but they are like $250+ if I'm not mistaken. Getting a short positive reset that some talk about is nice though, I just personally haven't felt one I thought was justifiable from Zev or Agency arms or anything *yet*.
I've owned about 20 Glocks over the last 20 years. Tried all kinds of triggers. The Vogel trigger is about as good as it gets. However, if I were you I'd sell the 19 and buy a Sig 320 compact. Really nice trigger right out of the box. If you want lighter the Grayguns trigger is really nice.
Personally, I'm trying not to "customize" myself away from being able to pick up a fresh stock Glock and be able to shoot it effectively.
I polish and use 3.5# connectors, getting the pull down to ~4.25 #'s. Also using trigger stops on a couple range guns with good success so far. Not quite ready to carry with the stops yet for a few more hundred rounds.