Co-owner for investment account or be a beneficiary for tax purpose?

I have an investment account.  Originally I was getting much refunds for both Federal and State before I added the information for my investment.  Then, once I added the 1099-DIV, the federal tax became much DUE.  I don't have that much investment, nor did I earn that much dividend.  Indeed, the amount of the dividend is many times less than what my tax increases.  That got me thinking WHY?  Is it because I solely own the investment but not joint with my husband while filing jointly???

 

1.  Would someone kindly explain how the tax differs between sole owner vs joint-owner for an investment account earnings.  Are there any differences when filing for the tax???

 

2. Would it actually better to have a joint investment account than having my husband as a beneficiary regarding tax perspective?  I am not sure what "if one contributes much more than the other account owner, then IRS would treat it as a "gift" means????  If we both owned the same account, we put cash there for investment, but NOT a retirement at all??? 

 

Thanks much for the help