If you interested in my opinion, Nova looks more user-friendly (better documentation, scaffold-building) and better oriented for third-party customizations [and without third-party they looks very poor], but it has significant disadvantages also. The Sharp-panel realization is more flexible really. Generally, the sharp lacks support for “details view” mode (as for read-only) — it possible to realize it with read-only text fields and html-fields, but it looks as dirty hack, and “cards” feature — as widgets with stat or custom content, that injected in entity list. Also a little bit more kind of fields in core (DateRange, Code (code-mirror or ace-editor based)) will be very welcome