Nikon 24-120mm f/3.5-5.6G AF-S VR or Nikon AF-S NIKKOR 24-120mm f/4G?

Which would preform better or are they both at the same level

One thing you may have noticed is that the new 24-120 mm f/4 lens (which is also a VR lens) has the same aperture from 24 mm to 105 mm and is a FX lens, so if you ever do buy a full frame Nikon, it will cover the whole sensor and not automatically crop the image to DX which Nikkor lenses do when attached to a full frame Nikon camera

The old (2003-2010) Nikkor 24-120mm f/3.5-5.6G was designed to be an economic lens costing less than $600 new. Its maximum lens aperture a 24 mm is f/3.5, but at 120 mm it closes down to f/5.6, a full stop less than the new 24-105 mm f/4. The new f/4 version costs closer to $1,000.

The f/4 G with it's constant aperture is the preferred lens because when you zoom, you don't have to change your exposure.

You don't state whether you're using FX or DX bodies. If DX, then skip the FX lenses (unless there's no equivalent in DX) and stick with only DX lenses. DX lenses are optimized for DX bodies and will produce a sharper image than using an FX lens on a DX body. Here's a video explaining why this is:

To see how well these lenses perform go to photozone.de

The newer, more expensive f4 is is better. But for what? If you have a DX camera you pay a premium in weight, bulk, money, and even in quality to be able to cover the FX sensor. There are DX lenses that are better value.
If you have an FX body, the 24-120mm is not bad, but not fabulous. It will have some corner softness on the FX frame. Getting not just coverage but actual sharpness on an FX frame (especially with a 36 MP sensor) comes at a high price. In the old SLR film days, on 4X6 inch prints no one would notice.