I’ve been shooting with Nikon cameras and lenses exclusively since 1979. Why? Because when I bought my first Nikon (an FM), it was what anyone who considered themselves to be a photographer was using (outside of medium format, of course).
If you shot 35mm, you shot Nikon. Period.
Over the years, I have learned that Nikon gear really is top notch. I still have those original Nikon cameras and lenses, and they all still work. The lenses aren’t up to today’s standards of sharpness and clarity, and there was no autofocus or auto exposure back then, but they are still mighty fine pieces of glass.
The more recent crop of lenses are some of the sharpest optics I’ve ever worked with. The camera bodies fit in my hands like they were designed just for me, something I can’t say about any Canon I’ve ever touched. And I find all of Nikon’s gear to be pretty rugged. I’ve dropped cameras and lenses, and they keep working. Have I ever had to have something repaired? Of course. As rough as I am on my gear, some of it does end up in Nikon’s repair shop from time to time, but even then, their service is great, prices reasonable, and the turnaround time is fast.
I think, though, what entices people to switch is the idea — like it or not — that if they switch, they will suddenly become better photographers. Not many people will admit to that, but it’s still true.
The problem is that they make this sometimes monumental change, and then actually do see a difference in their work.
Has their work actually gotten better? Sometimes the answer is yes, if for no other reason than they are now shooting with the latest technology. But even if it's not better, it looks better -- because they spent all that money making the switch.
I know that when I upgraded from a Nikon D2h purchased in 2004 to a Nikon D810 purchased in 2015, the quality of my photos took a huge leap forward -- because in the 11 years that had passed since the D2h, the technology had improved so much it wasn't funny. With the D2h, I couldn't shoot above ISO 400 because of the noise. With the D810, I can easily get to ISO 4000, and were I to upgrade to a D850 or a D5, there would be a quantum leap in noise improvement. Likewise, when I moved up from the older Nikon AiS lenses to the newer glass, my work made another leap forward in quality.
Had I switched to Canon instead of buying new D810s, my work would have improved, for the simple reason that those D2h bodies had passed their 10th birthday, and their technology was terribly outdated.
But not because Canon makes a superior product. Their products are very, very good, but not superior.
I have a friend who recently sold all of his Nikon cameras and lenses and made the switch to Fuji. When I asked him why, he told me that he was at a point in his life where the smaller, lighter Fujis made his life a lot easier.
Notice that he didn’t say it was because the Fujis gave him better images. His reason, as he stated it to me, was that the Fuji cameras and lenses were smaller and lighter and therefore, easier for him to carry for long periods of time. Okay, I’ll buy that (even if he is 10 years younger than me). But he’s him, and I’m me. If switching to what he feels is something that will make his life easier, I’m glad for him.
On the other hand, I have another friend who "grew up" a Canon user. Second generation, if I remember right. An excellent, excellent photographer.
Then one day, she picked up a Nikon D850, and one lens (don't remember which one), and the next day, she put all of her Canon gear up for sale, and hasn't looked back. Why? Simple -- she likes the results better. Have her photos improved? In one very real sense, yes. The D850 has features that allow her to get what she sees in her mind into the camera, and which in turn has allowed her to take her ideas to not just the next level, but several levels higher. Her images were great before, but are much, much better now, without nearly as much post processing.
As for me, were I to feel a need to make a switch for that reason (and the day may come when I might feel that need), I would switch to a Nikon mirrorless -- because I'll be able to use all of my current lenses. But as of right now, I don’t see a need. I’ve been shooting with pentaprism / mirrored cameras for so long there is nothing about them that bothers me. My D810 bodies both have MB-D12 battery grips, and Really Right Stuff L-Brackets, all of which add considerably to the weight, which, as of this writing, doesn’t bother me.
This brings up another point: I just don’t have the finances to buy more cameras or lenses, which begs the question -- where are the people making all these switches getting the money?
When I buy more gear, it must meet three criteria — it must be fully compatible with what I already have, the money to pay for the new gear must already be in the bank, and I must have a real need for whatever it is. For me to dump my two D810 bodies and replace them with two Z7 bodies with FTZ adapters is, at present, not just financially impossible, it’s financially irresponsible. I don’t NEED a mirrorless camera. (As a member of Nikon Professional Services, I could have them send me a Z7 and an FTZ to play with for a couple of weeks, and since I have a vacation coming up in a couple of months, I might just do that, but I’d still have to pay the shipping both ways, and I can buy other things with that money.)
So for me, the question becomes, if money were no object, would I make a switch?