John, are you sure you don't regret your MP-E 65mm as macro photographer ?
You are an insightful person, Rosko
It was the MP-E 65mm that actually kept me with Canon for so long ... did
not want to abandon this lens
The trouble was, my 7D was sooo far behind, in sensor technology, that I began to grow impatient for a replacement
When Canon came out with the 7D Mk II ... I was underwhelmed. It did
literally nothing excellent.
Brand new, the 7D Mk II was already mediocre. All it did was burn so-so images faster than its predecessor to the memory card.
I figured I would wait for Canon's next 5D ... and the 5DSr came close to tempting me ... but it, too, was (essentially) a giant, high-res, but (ultimately) mediocre sensor.
That was when I ditched my Canon cameras and moved to Nikon.
There is no equivalent in Nikon system and unfortunately no compatibility or adaptability between Canon lenses and Nikon body. 
No equivalents, true, but there are workarounds.
For one thing, the MP-E 65mm isn't a truly high-quality optic; it is only convenient. For another, it is useless for anything but macro.
In discovering Nikon still had the AI and Ai-S manual lenses, that could be reversed and still retain aperture control, I found my solution to the problem of "how to do" high-mag macro work ... just use Ai-S lenses, reversed
The glass quality of the better Ai-S lenses is at least as good as the MP-E, and I can orient them properly and have decent wide-angle lenses.
Here are a couple shots I took with a 28mm,
reversed, for 2.4x lifesize:
Even when I had the MPE, I rarely went over 3x lifesize ... I was usually in the 1.5 to 3x lifesize range, so between my 50mm and 28mm AI-S lenses,
reversed, I am good.
(Beyond 3x, you need a studio, really).
No Nikon bashing intended, though ! 
I do bash Canon a little bit, because I was a big fan of theirs. When the 7D first came out, it bested Nikon's D300.
However, Nikon quickly came out with the D3x, and then the D700. When it came out with the D800/D810, Canon sensors were pretty obsolete ... and a lot of people switched.
I eventually switched too
Sony was a very, very attractive alternative, offering greater lens interchangeability than either ... but I really don't want to fool with adapters.
(By themselves, Sony doesn't have much in the way of lenses; Fuji even less options.)
The reason I went with Nikon is their virtually-limitless options ... and everytime they come out with something new, they set a new precedent.
When it first came out, the D810 blew everything away.
2.5 years later, the D810
still has the best base ISO capability.
The Nikon D5 and D4s lead in high ISO capability.
The D5 and D500 both have industry-leading 3D AF tracking.
Every single FL super-telephoto lens Nikkor has made beats every single Canon equivalent.
Unlike the 7D Mk II, Nikon's D500 is a benchmark pretty much everywhere in its class.
When the 7D II came out, it won a Silver award at DP Review.
When the D500 came out, in won a Gold award, Best High-End DSLR, and Best Overall Product, period, for the whole year.
Nikon's technology is exciting ... not disappointing.
Companies like Sony and Fuji pretty much appeal to folks shooting "normal" stuff (landscapes, portraits), as all these companies offer are "normal" focal length lenses and that's it. Fuji has nothing to offer a serious wildlife shooter. Nothing. (Sony's does have some super-telephoto lenses, but they are ultra-expensive, and totally inferior, to Nikon and Canon super-telephotos. Sony super-telephotos are based on the elder Minolta designs and are junk by comparison to Canon and Nikon's best.)
For sports and wildlife, Canon and Nikon are the only truly complete options.
Canon and Nikon have equivalent super-telephotos, but Nikon has the edge.
Nikon also has the better sensors as well as better AF systems.
Every edge goes to Nikon over Canon for wildlife shooting ... except the 1DxII has better 4K video.
Canon's MP-E 65 was a definite edge, as a
lone tool, over Nikon ... but Nikon's other macro lenses are better than Canon's, and Nikon's sensors are better than Canon's, and (by reversing AI-S lenses) I can get the same "beyond 1:1 macro shots" as I could with the MP-E ... and I get to capture my efforts on a better sensor.
Cheers,
Jack
