There are some benefits to replaceable styli also. The stylus is easily replaced without need to send it out for re-tipping. And with some cartridges, such as Goldring, the styli are interchangeable, so you can move up in the line, to the Gyger Line-contact types, without buying a whole new cartridge.
IMO, if you find a cart you like, at a price you like, and it has a replaceable stylus, don't worry about it. But if you are looking for a true high performance cart, then the non-replaceable stylus is the way to go.