The difference is not always clear
Started using a new porcelain slip today. I have been using slips from @bathpottersupplies for a while now. Whilst their packaging is a little over the top it does at least use items I can recycle, so I'll forgive them that.
The slip itself is always very good quality, and I love the tubs it comes in, rather than screw top can type containers that some companies use. Those always make it difficult to decant the slip.
Anyhoo - the new porcelain slip. I've been using Bath Potters special porcelain, and had some good results - see the lithophanes with this post.
Now I'm trying their Parian casting slip (https://www.bathpotters.co.uk/parian-casting-slip/p4741 ). First thing I notice is how much faster it dries and is ready to be removed from the mould. Also it is a little more brittle than the special porcelain slip. But also, it seems to give a higher definition to the moulds.
Another useful factor here is that this porcelain has a slightly lower temperature for 1200-1240 oC for translucence compared to the special which is 1240 oC - 1270oC.
Once I fire the piece I'll give an update.