Technical Early 80's Taiwanese JGA copy vs Devilbiss JGA 502

Hello All. So I've had this gun since the early 80's, Went to the my local body supply store looking for a gun I could reserve for spraying primer exclusively. The store owner recommend this one. Don't remember what I paid for it ,must have been pretty reasonable.
Fast forward about 45 years. tried to spray my steel gate with water based Rustoleum gloss black. I ***umed it was sprayable directly out of the can. Well, it was not. Tried spraying this stuff with my Purple 20.00 HF HVLP had to thin it down so much, after drying, it peeled right off the metal panels. Went back over it with oil based Rustoleum (still had to thin it down quite a bit) but this time I decided to breakout the old Taiwanese made gun and was quite surprised how well it sprayed.
After some research online, this gun looked strikingly similar to a Devilbiss JGA. Google confirmed, who ever this Taiwanese manufacture was, they did produce JGA copies back in the day, it stated some parts were even interchangeable. Sure enough, the air cap threaded right on a Devilbiss MGB series 510 gun I had just gotten a hold of. During a through cleaning, even the internal workings appeared as quality machining/components.
Finally, can any of you Guy's and Gal's share any of your own experience/s ? Between how either of these guns performed in comparison?

 

I have the same spray gun that I bought in the late 1980's to paint my 29 coupe, still have the gun and the coupe. I used it for years until I decided that I needed an HVLP and the old siphon gun still lays paint better. It's still hanging on the shelf in the garage, you can see it behind the ch***is for my 30 coupe.

 

I miss my old spray guns, but the cost of paint now days an HVLP is a must have.

 

Complete frame off restoration? How cool is that. beautiful car beautiful work. Congrats

 

I’ve done a comparison between hvlp and siphon at school. Gravity feed vs siphon.
Both look very similar/laid down paint nicely
The siphon wasted a lot more material

you don’t spray em the same.
HVLP looks like **** when sprayed like a siphon. Same when you do the opposite.

 

The frame in the picture is from my 30 Sport Coupe, the 29 is stashed in another stall. I've done 5 Model A's and painted 3 of them with the knock off gun, went to a HVLP and never been real happy with the final product. I always have to cut and buff with the HVLP.