Range permitting, the 6 minute vectors provide quicker mental calculation of speed.
True 6min vector (TV6) of 0.75 NM indicates the target's true speed is 7.5 Knots, the direction of this vector indicates the vessels heading relative to the tracking vessel or its electronically fed heading if one exists.
True vectors allow users to determine the aspect of a target at a glance, something otherwise requires manual plotting.
[1] Manufacturers use a variety of acronyms for the small crafts or yacht, e.g. MARPA (mini or manual ARPA, depending on which company you talk to) is the dominant one.
The major difference of this Radar plotting aids may not be fully equivalent to all ARPA performance standard of IMO approved type which is a mandatory requirement for large ocean-going ships.