You better take both, the USQ-78A by itself won't find a sub in a century.
I must differ. By itself, it is much more user-friendly than the UYS-1, which in and of itself is worthwhile. The 78-B and C upgrades are even better. Oh, and after that's been all wrung out, the next step is an even MORE advanced processing and display system, one we're all salivating for.