Can't say about
madvapes, but I know that Wordup carries good quality. I've used them to make feeder adapters for REO's; modded them for volt meters, and used them in PV's I've made....never had a single issue. But, that's just my experience....other folks may have different luck
Adapters
Every time you use any adapter the insulator/gasket gets compressed. If it's thin it's easier for them to split. I'd rather spend 4 bucks at WU and have more confidence in their performance.