Bitcoin has uses that Silver does not, I am sure it is safe to say that most people on here especially those early adopters have access to Paypal and credit cards but there are MANY people out there who do not and probably never will which means they have a very hard time buying through the Internet.
Well bitcoin is a new way for those shut out of the traditional banking system to have a way to shop online, obviously there is a long way to go in terms of more businesses accepting Bitcoins but as they do more people will seek to acquire bitcoins which in turn will increase demand and most likely price.
Is Bitcoin mostly an investment type of thing now? I think it is safe to say yes but that is starting to change and as it does more demand usually translates into higher values for Bitcoins.