Pick the lightest tire.Both have pros and cons, but i would prefer the option which would have the least affect or wear of the vehicle, i.e. transmission, bearings, etc.
Pick the lightest tire.
Edit: Looking at the spec sheet for the Lattitudes, it looks like your best option there would be a 235/55R19. They're close to the lightest tire that would reasonably fit the CX-5, and they'd also have the advantage of making your overall gearing taller, so that your engine is turning slightly slower for a given travel speed.
"they'd also have the advantage of making your overall gearing taller, so that your engine is turning slightly slower for a given travel speed."
If you're only replacing two tires, then yeah - you need to stay within 1% of the other tires. If you're replacing all four tires, the AWD system doesn't know the difference.
And as for your second point, sometimes the best way to learn is to ask questions.
The 235/55R19 will have a lower revs/distance rating than your stock tires. This means that the axle shaft is making fewer revolutions for the same distance traveled down the road. Your entire driveline from the axles all the way back up to your engine will be turning more slowly at the same ground speed compared to your stock tires. You're not likely to notice the error in your speedometer (~1 kph at highway speed) but if you're concerned about longevity of your other components, it does provide a benefit, there.
I can't really blame Mazda for putting the warning in the owner's manual that you shouldn't change tire size - I've seen some wildly oversized tires put on vehicles, and that can be very bad for equipment. Your stock wheel and tire weighs about 27 kg. There are plenty of wheel and tire shops that would gladly sell you aftermarket equipment that not only weighs 10+ kg more per wheel, but drastically increases your rolling diameter. This puts more strain on suspension components, leading to failures. Owners will try to get Mazda to pay for the damage they cause, and neither Mazda nor their dealers want to deal with that. Greatly increasing tire diameter will also slow acceleration noticeably, leading to more customer complaints. It's not like Mazda can just say in the manual "Be reasonable when replacing wheels and tires," nor can they give a table of acceptable replacement sizes, since then somebody will inevitably replace only one pair of tires with one of the listed sizes, and end up damaging their AWD system. It's far easier for Mazda to just say 'Don't do it' and be done with it.
I'm not sure what would change my mind - I said that a 235/55R19 would fit just fine on your Akera, as long as you're replacing all four tires.
When wheel-size lists 7.0" for a 225/55R19 and 7.5" for a 235/55R19, they're giving the standard wheel width that's used in measuring mounted tire dimensions. I'm not entirely sure what's up with them giving 8.0" for a 245/50R19, since that size's standard measuring wheel is also 7.5" wide.
I made a thread a few years ago where I listed the acceptable wheel width range for every size I could find that fit the first-generation CX-5. That information is still valid if you want a quick reference to determine whether a given size will fit your stock wheels.
Im not going to be a lot of help with model recommendations. Theres not a lot of overlap between what you can get there and whats available in the States. The only ones that I see on Errols site that Ive seriously considered are the Pilot Sport 4 SUV and the Falken Azenis FK510. Maybe check out http://www.tyrereviews.co.uk/ - I think theres a lot more options available in Europe that you could also get there.Which of these options would you choose as a top 3
After having the chance to play with the wheel-size calculator, I'd say that it's better than a lot of tire calculators you'll find on the 'net, but it's far from perfect. The first big issue I see is that when they give a backspacing number, they're giving the inboard extent of the tire's bead, not the flange of the rim. The actual backspacing number will be about 13 mm higher than what they state. The bigger problem is that they don't account for the fact that a mounted tire's dimensions will vary based on the width of the wheel upon which it's mounted.Wheel-size.com is actually a good indicator...
https://www.wheel-size.com/size/mazda/cx-5/2015/
After having the chance to play with the wheel-size calculator, I'd say that it's better than a lot of tire calculators you'll find on the 'net, but it's far from perfect. The first big issue I see is that when they give a backspacing number, they're giving the inboard extent of the tire's bead, not the flange of the rim. The actual backspacing number will be about 13 mm higher than what they state. The bigger problem is that they don't account for the fact that a mounted tire's dimensions will vary based on the width of the wheel upon which it's mounted.
I've often suggested that anybody who wants to learn about tire sizing should start by reading a few of the articles on Tire Rack's Tech Center. Barry's Tire Tech is another good resource that goes into detail on why things are the way they are with tire and wheel sizing.