We know two things for sure :
1) WC has not tried/heard ricevs suggestion with inverters, so he cannot absolutely say that one is better than the other. He can speculate.
2) ricevs has not tried/heard a stromtank, so he cannot absolutely say that one is better than the other. He can speculate, but he's indicating that he is interpolating - based upon a reviewer's comparison of a Stromtank vs. an inverter, then comparing other products to what the reviewer used that are supposed to be better products.
The way I look at it, anything is possible, but when putting pieces together as ricevs is suggesting, synergy will come into play, and the end product might or might not be as good as he suspects.
With that in mind - I see that ricevs mentions that he does not mind begin wrong about his speculation that this DIY setup would be better than a Stromtank. That indicates to me that he is open minded about the comparison. To me, this is respectful and an interesting option - it would be fun for someone to try it out. Even better for all of us if WC tried it.
All of this is regarding the performance side of it. Regarding the appearance side of it, the form factor of the Stromtank wins in my book and most likely with my wife :-)
Dave