What does "value" represent?
I think they're both good. Ideally this is a site about marketing and sales for the video game industry. It's important to understand both the profits as well as the number of sales.
This is more important now because some HD games are moving to different profit models. I.E. Dragon Age is moving towards a DLC / Expansion model. In this case the unit sales of the original game could be argued to be more important because the units sales becomes the market for the DLC.
In other cases, the value is more important, like front loaded games.
Also, it would be interesting to see long term value sales. Since a lot of times games are boosted from bundling and sales. Just because a game has good legs doesn't mean that the company earns the same amount of money.