Main differences between Nikon lenses // 55-300mm - 70-300mm?

I'm trying to decide between these two lenses to use with my nikon D5100.It would be used for various things from portraits of people, animals, a few outdoor animal action shots (nothing super amazing, just of my own animals) landscapes e.t.c. Just for my own enjoyment.

I know that there's quite a price difference between them, and from what i have read i'm thinking of going for the 70-300 lens, but is the extra cost worth choosing this one over the 55-300? What are the main differences between the two? I currently only have the 18-55 that came with my camera. Any info and advice hugely appreciated.

There are more than one model of the Nikon 70-300mm so I want to make sure you are referring to the $589 AF-S 70-300mm and not the $175 Nikon AF 70-300mm which will not focus on your D5100.

There are a lot of differences between the 55-300mm and 70-300mm lenses, the first and foremost being the 70-300mm is a FX lens, while the 55-300mm is a Dx lens. While both lenses can be used on your D5100, if you are ever thinking of upgrading to a FX body someday (i.e. D600 etc), then you will want the FX version. This is probably the most significant cost difference.

In fact, using FX lenses on a DX body often results in better performance over Dx lenses as you are only using the "sweet spot" center of the lens. As blur normally begins on the edges of the lens first, you will still have that issue with a Dx lens, but not so much with a Fx lens on a Dx body.

Also, the 70-300mm has ED coating and is internally focusing, whereas the 55-300mm is not. And finally, the 70-300mm has VR ver 2 (active and normal VR), while the 55-300mm only has VR version1.

All added up, the 55-300mm is an entry-level lens while the 70-300mm is a semi-professional lens.

Here is some test data on how both lenses work on a D5000 (the D5100 has not been tested yet). You will see that the score for the 70-300mm is slightly higher.

http://www.dxomark.com/...ra2%29/587

And there's good news about the price. I bought my AF-S 70-300mm as a Nikon Factory Refurbished lens at a huge discount:

http://www.adorama.com/...AFVRR.html

At a refurbished price of $359, it is a no-brainer to buy the 70-300 if you are worried about price. I have purchased several Nikon factory refurbished lenses without any problems at all. It is a good alternative if you want to save a few dollars.

I have the 70-300mm lens, to be specific it is the 70-300mm f/4.5-5.6 G IF-ED AF-S VR.
Most reviews of this lens rate it highly, as do I. It is very good for photographing things that you can't get close to such as wildlife, motorsports etc. It is a bit heavy to walk around with when you are just 'out and about'.
It is not really a portrait lens and neither is the 55-300mm, the 18-55mm you already have is much better for that. If you want to do portraits or photograph objects that are near you and leave the background out of focus then I would recommend looking at the Nikon 50mm f1.8 G.
As always I recommend going to a good independent camera shop and try the lenses before you spend your hard earned cash on them.