Solo may be a better choice if your only goal is to grind. I don;t argue that the modes should be equal end equivalent, I say that the field is leveled because everyone has equal and equivalent access to all of the modes. If you are looking for some PvP action, Open is surly the way to go. If you want to concentrate on a PvE goal, open may be better suited. That you feel that open is your preferred mode, then you have to accept the results of that choice.
There is a parade of "where is everyone", "where can I find a fight", "we need to incentivize open" threads. I dare say just as many "I got ganked, so I'm going to solo" threads. I've seen open referred to as a "wasteland', 'ghost town', and 'deserted' by others frequently, so I think you may have to readjust your view there.
In this thread alone, there are a number of players that have said they just plain prefer solo. Because of connections, disabilities, shyness, or just a quiet place to wind down from the trials of everyday life. There is even a large group of players that expected to get a completely offline version of Elite, but were offered SOlo as a reasonable substitution. Players may just prefer to control the people who they interact with. That's all we're talking about here. Just a choice of whom we spend our game time with.
You must have skipped the myriad posts in this very thread, and/or it's cousins, expressing that very sentiment. Read back through the Threadnaught and you just may change your mind. The 'I'm going to solo' threads aren't from established players who fear an insurance claim. It's from new players being preyed upon by the bullies looking for an easy kill. It's not hard to understand their motivation. Leaving the modes available to all even gives those guys a later chance, when they have their 'space legs', for some revenge. When I want to mix it up with other commanders I have to jump dozens of times to find anyone up for a fight.
What extra risk there may be in open is totally selective. You can, as evidenced by many posts, effectively play 'solo' in open if you avoid the hot spots. SPace is vast and many times this thread has been given advice on how to 'stay safe' in open, just to encourage participation. The fact that the games instancing rules can 'hide' you from potential adversaries for any of the uncountable reasons within the matchmaking code, brings the risks in open and solo much closer together. Finally, with the 'submit, boost, jump' mechanic firmly in place, just about anyone can avoid combat more often than not. Any extra risk in open seems so minimal, to an experienced player, that it hardly deserves a reward.