It depends on if you are one of those people saving their silver for the collapse of society as we know it...
Bitcoins can be instantly sent around the globe. Silver, not so much.
Bitcoins cannot be counterfeited. Is there a touchstone for silver?
Bitcoins can be quickly changed for other currencies. Where do you take silver at 3am?
You can't press 'delete' on all your silver.
You can make shiny things out of silver.
If we just consider silver an asset you can use to buy computer hardware, and bitcoins an asset you can turn into paper money, the above doesn't address your main questions, which are:
1. Is mining bitcoins a good return on your investment?
You may eventually pay for your computer "shovels" used to mine, or more. You may barely pay for the electricity you use. You at least have a reason to get a cool video game rig.
2. Are bitcoins good to invest in long-term?
Nobody can answer this except the flying spaghetti monster, and since she doesn't exist, she's not giving up her secrets.