The tuner differences between the tuners targeted for the amatuer SSB
users and the commercial
ones are relatively small and may be insignificant to cruisers. For instance the older AH2 and the AT120 differed mostly by the addition of a plug-in LED board on the AT120 which allowed installation
techs to log down the reactive component relay positions for each memory location or for a particular frequency once tuning is achieved. Should the auto tune feature become damaged then one could merely set the switches manually to light the appropriate LEDs for that freq and have a "tune". The AH2 would not do that.
The later tuners have slightly different power handling capabilities and some reactive (mostly inductor) value differences mostly to allow lower source impedance at or near 2 MHz (where small vessels have almost no "reach" with their small geometry antennas).
So, in general, cruisers using 4MHz and above with either relatively short transmit times at full power or power limited to around 120W PEP will probably not notice any differences between the AT120, AT130 or AT140.