I agree with your statement but one thing that a pure bitcoin investment cannot do is pay dividends every week to the owners of bitcoins.  If bitcoins continue is appreciation other people might buy into bitcoin at increasingly higher prices but a mining fund would consistently get more bitcoins from their initial investment.  This fund was hit when more shares were used to purchase the BFL ASIC.  It cut the dividend per share because their were extra shares but no extra incoming revenue.  At that point the dividend being paid out could not be the only metric for the book value of the fund.  There is also the value of those ordered ASIC that need to be taken into consideration when pricing the fund.  There is also the bitcoins held in reserve that the fund has.  It may use those bitcoins to purchase more ASIC but it could also just pay a large dividend as well if that is more beneficial.  Another important thing is how the fund is well managed.  Just look at some other funds (ex. BITBOND) and see how much risk a bad manager can add to your investment.

I would not be surprised in the future that as the ASIC are delivered and as the fund grows less of the fund's bitcoin revenue will need to be held in reserve for future growth.  Once the fund becomes a growth fund then investors will not have to worry about share dilution and their initial investment may outperform bitcoin's rate of appreciation.