General opinion on these seems to be that the Camillus version is a little higher quality than the Ontario, which has had some problems reported with the consistency of their heat treat. Take that with a grain of salt. Design-wise they are very close, though I think the Camillus has a more fragile tip. I filed mine down a bit to a more drop/spear point and prefer it that way. One problem is, Camillus is for all intents and purposes out of business and the 5733 is going to get scarce real soon. If you want one, get it now. I have one of each and prefer the Camillus, but really they are pretty close.
The tang passes through the handle inside the leather washers and through the butt cap. If you look at the end of the handle you can see the rectangular tang. The butt cap is pressed down to compress the washers and the tang is hammered to spread it out, same idea as a rivet. Now it is larger that the hole in the butt cap and locks it in place. I've never heard the Ontario's are welded, I thought they were made the same way. Sure look that way. I wonder what type of welding they could use that would not fry the leather washers, probably more high-tech than these knives would get.
Hope this helps. I'll try to post some pic's later if I get a chance.