Of course price could be a factor in this comparison as well....

Of course price could be a factor in this comparison as well. This remains unknown at this point in time!

There may also be an advantage in predicted lifespan. I keep an eye on ADO which is involved with a couple of battery companies where the aim appears to be to increase the Si content of electrodes to increase energy storage of Li batteries. Up to this point at higher Si %'s, electrode decomposition has posed serious limits in the no of charge/discharge cycles that could be undertaken and I get the impression that problem applies with the bigger batteries too. Of course if ADO's coating product or some other technology successfully overcomes this limitatio,  any advantage accruing to the VRFB guys may be lost. 

Please DYOR on these aspects