Hi, I'm new to the area but from what I understand snRNA-seq is used for frozen tissue due to the low viability of the individual cells once defrosted making them unsuitable for scRNA-seq.

I've read a number of papers comparing the preservation of singe cells for future scRNA-seq with methanol fixation & DMSO-based cryopreservation both having their pros & cons. I suppose it ultimately depends on your cell / tissue type.