As mentioned above, they are like 4wd brands - everyone has something different and has an opinion.
It simply depends on what your needs are. Canon, Nikon, Panasonic, Sony, Pentax et al are all fine for SLR. Personally I've shot with a Pentax for 20 years, film and digital and muchly prefer them over the others - no other reason than personal preference. Canon and Nikon have the biggest market share namely due to marketing budgets, but it doesn't mean they are any
better than the others.
As each brand has multiple products, what features do you want?
MP size is the first thing we see. Do you need 30MP or is 12/16/18MP enough? Poster prints, more is better. 6x4 prints, or display books less is satisfactory. At 16MP my pics are also around 10mb each in size, so also consider the storage capability of your computer. The bigger the MP, the bigger the photo file size. (I recently installed another 8 TB of hard disks, on top of the 5 I already had)
Do you need all the wizz bang professional features?
Do you need manual controls, or will it always be left on Auto mode?
Sometimes its better to start with the basic and work your way up when ready.
But more important than the camera is lens selection. The lens is what can makes a good picture great. The 'better' lenses will be sharp, will be 'fast' (low aperture and allow good pictures in low light), might be weather proof, coatings on the glass to prevent aberrations.
Big zooms sound good, but it means the individual glass elements inside are trying to do too much, and you usually sacrifice image quality especially at either end, wide or zoomed max. Small zoom lenses are better. Primes, or fixed length lenses are best.
So consider the value of the lenses for how you want to use it. Is it better for you to carry around multiple lenses and swap them back and forth (also extra weight, extra handling, more risk of dust in camera etc), or will 1 be enough, even if it means (potentially) a lower quality photo. Most of the kit lenses (those which come 'standard' with the camera) are fairly low to mid range, but can be suitable to start with.
Personally I carry a fixed 15mm wide angle - landscapes and internal buildings etc; 17-70mm zoom - my general walk-about lens; 60-250 high quality zoom for wildlife; and a 300mm fixed - sharp wildlife. It can be a real pain swapping, but I can get some really good shots. The missus uses an all-in-one 18-200 and keeps complaining her shots aren't as good. At one point I had a 150-500mm but found it terrible for what I wanted. A good quality lens at 250mm will allow post production cropping of an image, potentially better than a lesser quality 500mm.
But a good quality lens can be a thousand $ or more.
Along the same vein, consider the
availability of lenses for the brand chosen. Pentax for instance will accept every lens they have made for the last 40+ years so there is lots around. Some might be a bit more hands on manual to use... but they are available, and some very good quality ones also. Canon and Nikon have lots available, but I think film era ones can't be used on digital (please correct me if wrong) . But I'm not so sure about Sony and Panasonic. Most brands have different lens mounts so they prevent swapping lenses across camera brands. But there are also plenty of lens manufacturers who make for all bodys and change the mounts to suit - Sigma, Tamron, Tokina and Samyang all make lenses for all brands and are very good - you do not need to have a Pentax lens on a Pentax body, or Canon lens on a Canon body if another suits. But I can't put a canon lens on a pentax body without an adapter. If you get serious you can always upgrade a lens later that you can then use for years on future cameras.
Whatever is chosen try to find a
users website for that brand. Like the expanders forum, I find Pentax Forums invaluable. I know there are also Canon and Nikon user forums out there also. Avoid the ones dominated by professional who expect you to have a Masters in Photography before they lower themselves to respond to you (reminds me of another caravanning forum really)
When shopping, go in to the stores and handle them. Take a memory card with you and take photos in the store to compare at home on the computer - don't rely on the screen on the back. Feel the weight, is your hand comfortable on the grips (some are smaller or larger than each other), are you likely to bump any buttons when you don't want to, or can you comfortably reach the buttons?
In the budget you mentioned you could comfortably get a Canon 750/760D, or the older 700D; a Nikon D3400, but I'd push the budget to a D5600 if possible; a Sony A6000 (similar to a 4/3 type camera with no viewfinder, but with a larger sensor like a DSLR); a Pentax k-50, but like nikon I'd push for a k-70 or KS-2 instead). Also maybe consider a sturdy tri-pod, spare battery or two, filters (UV and maybe polarising). Again like a car/4wd accessoritis can be a problem if you get seriously into it.......
A fantastic website is
www.dpreview.com which lists pretty much all cameras released. Most have reviews, both by 'professional reviewers' and users. And you can compare a large number of cameras against each other to cross reference their features etc. (Just be aware some like Panasonic Lumix have different names for their individual products depending on worldwide region). From what I can see, the website appears to be independent. there are also forums there too.
Sorry if thats more confusing than it needs to be.
If so, to keep it really simple... get a basic Canon 700D with 18-55 and 55-250 lenses and you shouldn't be too disappointed.