No one with a brain would argue that Victor is as valuable or less valuable as Branyan...for now.
At Catcher, Victor is a great, great player. At first, Victor is an average hitter, average defense and has well below average power for a 1st baseman.
Productivity and value are two different things. I'd rather have Victor than Marson, but I see no need to pine for Victor to play first base. Which is why we should have gotten something for him while we could, before he is strictly just a first baseman and he loses a shit ton of value.
And batting average is solely based upon hitting...using OBP and SLUG gives you a real value of a hitter.
If a hitter is a .300 hitter and only hits singles, is he more valuable than a .275 hitter who is constantly racking up XBH because he has an extra .025 on the other guy?