@SlivPTSSolo was literally a switch of a variable from 3 to 1, so technically A&D beats it in terms of changes. Then, I'd say the limited armor, medkits, shield batteries and weapon choice lead to a more unique experience than solo was, due to the fast ttk and less loot fest. Also, for new players, A&D may feel more rewarding in terms of kills and damage, providing a good reason for having this mode available often or even permanent.
Personally, I'd see both solos and A&D in a rotating list of 4-8 different modes, becoming available once every season or so.