Crap advice solely because of the bias shown towards Canon or Nikon.
...
It's interesting to read on these forums from Mac users when people ask for camera advice, when most users just simply suggest a Canon or Nikon and never leave the fall open for other brands.
Reminds me of the time people suggested I should buy a windows machines because it was the main player in the market. I thought, us Mac geeks being users of an alternative OS, we as its users would also offer alternative suggestions alongside the mainstream in order to be balanced.
There is nothing wrong with the top 2 brands, just be aware there are alternatives as well and with whatever you go with I hope your dad gets some good use out of it.
Reasons to buy Canon or Nikon:
1. Widespread availability of parts, accessories, lenses, etc. Anywhere in the world you'll find what you need for Canon and Nikon. Not the same for Sigma, Olympus, Pentax, etc.
2. Community support- Canon and Nikon's user bases are huge. Any problem that can come up has been documented and probably solved.
3. Neither brand is going to go away. Canon and Nikon's commitment to the DSLR is tied directly to their company's success, unlike companies such as Kodak or Fuji who have since decided to stop production of their DSLRs.
4. Quality doesn't suffer despite mass production. A prime example of this are the Canon L-series lenses. It's very hard to find comparable glass whose use is so widespread while at the same time maintaining near-universal agreement among professionals and amateurs of their quality.
Yes, other companies have unique aspects or features that might be desirable, but when it comes down to what's important Canon and Nikon just do everything else a little better. Recommending one of them might be a result of personal bias, but at least it's not going to have negative consequences.