My opinion, and others may vary, is that I prefer to get factory made loops if I can do so in the sizes and chain types that I want. I am of the opinion that "shop-made" chains are a bit of an unknown quantity, and can potentially be a safety hazard...
When you get a factory made loop, you can be about as certain as possible that the loop was assembled properly, using the manufacturer approved parts for that chain, on the appropriate automated equipment, to exactly the correct manufacturers specs, etc... Indeed it will probably be just about impossible to tell which link put the loop together - all the rivets will be identical, all the parts will be the same, and so on...
There's a lot less certainty with shop made chains - What is the skill level of the guy that put it together? What kind of equipment did he use? Did he use the exact parts reccomended by the manufacturer for that chain, or "whatever's in the parts drawer that fit"? Are the rivets properly formed, with the same tension as the other links? I could go on, but suffice to say that you don't necessarily have the same level of quality assurance at "Joe's Chain Shop" as you do at the <Pick Your Brand> chain factory...
This isn't to say that a properly made shop built chain is impossible, I'm sure there are a lot of people that DO make them right - but how do you know?
Shameful confession time - MANY years ago, I worked in the garage of a store in a small town, I did minor work on cars and OPE of all sorts, including chainsaws. I got a two minute lesson from one of the other guys on how to use the chainsaw chain breaker and rivet spinner (I had to figure out how to use the chain grinder on my own) with NO mention of how to properly make up a chain. THAT I KNOW OF, none of the chains I made ever broke, but I would chalk that up more to luck than any kind of skill on my part. I've since read some of the chain manufacturer's websites, and in 20/20 hindsight, I was breaking most of the rules... I have no idea if the master links I used were proper - I had "inherited" a big box of them, pretty well jumbled together, and several rolls of chain - I would just try different links until I found one that fit, and used it. If I couldn't find a link that seemed to fit, or if a customer just wanted a chain shortened a link or two, I would press out the pins on one side, and then re-use whatever was left of the rivets. I had no real idea of how tight to spin the rivets down, I just went as tight as it would go, then if the link was stiff, bashed it a touch with a hammer...
Maybe I was an exceptionally bad case, but these days I'd just as soon get factory made loops from Amick's or equivalent rather than assume that the guy making them up in the shop knows more about how to do it right than I did...
Gooserider