Hey Dave - they’re basically all identical except for a handful of SNPs, so you can pretty much pick any. Take a look at Andrew’s overall analysis here: Phylogenetic analysis of 23 nCoV-2019 genomes, 2020-01-23.
I might suggest Wuhan-Hu-1, which is on Genbank: https://www.ncbi.nlm.nih.gov/nuccore/MN908947