They are two different products. QBTC is a closed end fund and BTCC is an ETF. Both buy and hold Bitcoin and are expected to closely track the price of Bitcoin.
As a closed-end fund QBTC has higher fees, but has fixed units which it can increase through new issue or buyback. As an ETF, BTCC can issue unlimited units based on the inflows and will do so to ensure it is tracking the price of bitcoin. The benefit of owning QBTC is that it can unlock more value as it can buyback units when shares are trading at a discount to NAV or issue stock to take advantage of when its price trades at a premium to NAV - this has the net of effect of improving returns. With BTCC it will not return more than the price of Bitcoin.
For the average investor, it really comes down to fees and BTCC has lower fees than QBTC. I know Dan sold his QBTC and put it into BTCC.B and I will likely do the same at some point.
Mat