I've never used OshPark, I've done quotes several times as it would be nice to use a US PCB manufacturer but it never works out, their prices are never reasonable vs qty.
I've used PCBway a couple of times, I can't really remember why. I hate the appearance of their blue soldermask, it looks like paint. PCB quality is fine but I hate their customer service. They offer all of these additional services like machining and 3D printing. I had something that I didn't want to machine myself so I sent it to them. 9-11 days is now about a month with no answer, it'll be the last time I use them for anything.
JLCPCB on the other hand, I'm sure I've had at least 1000 PCBs made by. No idea what the previous poster is talking about, I've never seen an error on a PCB. I've made plenty of mistakes, but the only problem I've ever had with JLCPCB was ordering 10 4-layer PCBs sometimes they mess one up and they email me about it and I'll receive 9 with a coupon. I always order 10, cuz it's barely more expensive than 5 even if I only need 1. And I even sometimes order PCBs that are designed pretty sketchy just to test something as I hate sitting there messing with breadboards. I have some boards used in industrial machines that have been there for several years.....no problems