These both finished seasons recently so I thought I would comment on them. I much preferred Penny Dreadful of the two. It had a better cast, better writing, better production values and much better acting, direction and photography. JS&MN clearly suffered from a limited budget compared to PD. JS&MN had few and unspectacular special effects shots whereas in the finale of season two of PD they had Titanic scale visualisations of three different vessels at sea (did they get a three-for-one deal?) just to show three of the characters departing.
The darker and more adult tone of PD would have served JS&MN better than the whimsical BBC-costume approach they took. JS&MN had limited sets and locations some of which (faery in particular) looked very poor. The directing and photography of JS&MN was very basic compared to PD, and some of the acting was in bizarrely different register to the rest. Many of the problems with JS&MN could be attributed to lack of money, but it is surprising that the BBC cannot make genre drama as handsomely as Showtime. Of course the BBC has a long record of being bad at genre so this disappointment isn’t so surprising.