Choose between the Canon 100mm f/2.8L and Nikon's Micro-Nikkor 105mm f/2.8G

There are Nikon fans and Canon fans, and both will argue the benefits and advantages of the two brands. While there is no doubt that both manufacturers produce top quality products, if you are not yet decided which make of digital single lens reflex (SLR) camera to buy, it's a good idea to compare not only the camera bodies, but the lenses you will be using as well.
First you need to be sure of what you basic needs are. For instance, are you going to be focusing (literally) on nature? If so, are you going to be shooting landscapes of close-up pictures of bugs and flowers. Perhaps you want to take photographs of birds. Do you want to photograph people? If so, are you going to take portrait shots or are you keen to get in on the action and photograph sporting events. The beauty of a digital SLR camera is that you can use it for all types of photography, including those mentioned, and more. It will be the lens that you use that will change.
So let's assume you want to do some portraits and also tackle some challenging close-ups. What you will need is a good macro lens – for close-ups – that also has the ability to capture great portraits. Both the Nikon Micro-Nikkor 105mm f/2.8G IF-ED and the Canon 100mm f/2.8L IS-USM macro lens fit the description. But which is the best lens?

Nikon Micro-Nikkor 105mm f/2.8G IF-ED
This is a medium telephoto (or mid-distance) micro lens that is perfect for extremely close-up photography as well as portraiture, which of course isn't necessarily close-up at all. Like many of its other lenses, this one has internal focusing (IF) which enables users to focus closer and faster than they can with conventional telephoto lenses. It also enables quicker auto focusing. Like all its super-speed telephoto lenses, this Nikkor macro from Nikon is made with extra-low dispersion (ED) glass.
The lens, which was launched in 2007, produces super-sharp images, produces excellent contrast and really true color, and it works well in low light.
With a manufacturer's recommended retail price of US$984.95, it has the ability to autofocus from life size (1:1) to infinity.
On the down side, it sometimes seems to "hunt" while auto focusing, especially when taking macro shots in low light. It does, however, have a "limit" switch that helps prevent this from happening.  
This lens is suitable for professionals, semi-professionals and serious amateur photographers.

Canon 100mm f/2.8L
Launched in September 2009, the Canon 100mm f/2.8L IS-USM macro lens was the company's first lens to feature new technology in the form of so-called hybrid optical image stabilization (IS) system. Its claim to fame is that it can compensate for camera shake that so often results in fuzzy photographs. The letters USM indicate that it has a ring ultra-sonic motor built into the lens that enables it to auto focus a lot more quickly than other standard lenses. It also has full-time manual focus.
With a slightly higher manufacturer's recommended retail price (than the Nikon lens) of US$1,049.00, its macro focus ability is also 1:1.
Like Nikon's NIKKOR macro lens, this is suitable for professionals, semi-professionals and serious amateur photographers.
If you opt for Canon, also have a look at their earlier 100mm f/2.8 macro lens, launched around the same time as the Nikon lens discussed above. It's considerably cheaper and does the work almost as well.