I need a flash for my Nikon?

I'm looking to purchase flash for my Nikon D-5100. I would like to know which you guys think would be the best to buy. I was looking into the SB-600, SB-700, or even the SB-800… Are there any other options that I should be looking into. I'm looking for something good enough for inside and out side portraits.

If all you want is fill-in flash, the little SB-400 is fine. Go for the SB-700 if you need bounce or the extra power or faster recycle.SB-700 also works better with multiple flash setups. Forget the SB-600 unless you can get it really cheap. The SB-700 effectively replaces the SB-600 and has a better user interface.

As you aren't talking about multi-flash setups and you are doing portrait, I doubt you will need the extra power or multi-flash + multi-group handling capabilities of the SB-800 or above.