Yup, i3 (along with i5 6xx) are intel's new dual cores and they are substantially better over C2D (assuming you mean Pentium Dual-core). If you mean Pentium D or Pentium 4 then you are a couple/few generations behind bud.
They (new intel dual cores) also have HT which provides 2 more 'virtual(fake) cores', which will help in multi-threaded apps.
droid it depends on what you want to use it for. I mean as much of an amd fanboy as i am, I will admit that if you are just gaming. The i3s are a better choice or go for an i5 even 750... if you choose any other 750 i will be disappointed. BUTTTTTT even though that is cheaper than newegg, meaning the i3 ur looking at. At that point of 139.99 I would spend a little more and go for AMD, to be honest at the price, I'd spend 20$ more and get a AMD Phenom II 955 Its 160, aparently at your store 165.99 If you got a local fry's or you can use a credit card go to newegg. But umm... At that price point i'd spend the extra 20 and go to 955, because with the 955, the AM3 mobos actually have mobos that run 2 PCI Express 16x 2.0 at full speed. While the 1156 mobos all run one 16x and one 8x some even 16x 4x. BUT If you do go with intel thatd be a firm dual core solution. PLUS the 955 is quad core so if you ever video encode
I agree with Aznshinobi because I am a fan of AMD. AMD proccesors are very unique and just as powerful as the Intel proccesors. They just cost less and I am actually going to buy a new desktop from HP that has a 4x phenom II processor and plently of RAM. The 955 is definetly a good choice but... it really depends on what you are doing and you can always upgrade to a bigger processor.