The quality of various bar pins, is an issue that we have gone round and round on with suppliers and customers. They all look the same, but let me just make a few observations. Starting with very inexpensive pins. These are made from just a bent piece of metal. Something like you see on a paper name tag. Often sold under the moniker "easy lock" as they do not have the safety catch. They are indeed easy..... but can open unexpectedly at times.
Moving up to a pin with a safety clasp we can still find extremely cheap base metal bar pins. These are made in China. They will be plated and the price is right. Your going to get these if you buy at Walmart, Michael's, Hobby Lobby or any of the huge chains… Yes they are inexpensive, but there is going to be a large percentage of bad ones. In the past we experienced 10%-40% defects on these. The catches won’t work correctly and they seem to often fail just as your potential customer is trying on your brooch. This is not a pin you want to put on a piece of hand crafted jewelry.
The next level up I would describe as good or medium quality. Generally these a brass. They are going to be pretty reliable. There may still be the occasional bad pin but overall it is a pretty good defect rate. You might pay .25 for one of these as opposed to the cheapo which might be .05 So for the extra .20 this level is the one I would recommend on most fashion jewelry.
The last group of bar pins I put in the superior or best category. Made in USA. These are constructed of solid nickel components. There is no plating and as such are not available in a gold finish. They have smooth acting clasps and strong thick pins. So thick in fact that on the larger size 1.5" some people will complain that the pin may be so big that it creates a hole in the fabric. Aside from that issue they are notably better and of course much more expensive then other pins. Expect no bad pins at all in this group.
People ask me why pin backs have holes in the bar. Most pins will have 2-3 round holes. This helps if your using a rather thick glue like E-6000 that will ooze up just a bit through the holes. If you were soldering the pins, the holes are also helpful in flowing solder into. Keep in mind, IF the pin back is plated, and most are, you can only use low temperature, soft solder. Using "hard solder" will require a solid nickel, brass or silver pin ( not plated)
Pin backs with prongs on them are meant to be mounted through fabrics and paper. In addition there are bar pins with bails attached so the jewellery can be used either as a pendent or a pin. The list goes on. Generally I would say the two an three hole bar pins are going to be the most popular and versatile as they can be used for gluing and some solder operations.