The safest carseat is the seat which is a good fit for your situation, and is installed & used properly every time. Vehicle interiors, carseats, and children all vary in 'design', so getting the safest seat for you is a matter of getting a seat that suits the size/needs of the child and the design of the car. A short heavy child may be safer in a different seat than a long lean child. A car with a very reclined backseat is going to hold a carseat differently than a car with a very upright backseat etc.
All carseats in Canada have to "get an A if they want to play"; they all have to pass the same basic safety standards. There is no grading within that testing and there is no ranking or comparing of seats – the seat either passes or it doesn’t. That being said, at this time carseats in Canada are ONLY tested in frontal collision scenarios at 48km/h – this is called Dynamic Testing. Carseats are not tested for rear-impact, side-impact, or rollover collisions, and they are not tested at higher speeds. Transport Canada also tests how much force is needed to release the buckle pre & post dynamic testing and how well the padding protects the child in a collision. If a carseat manufacturer intends for their carseat to be used on airplanes as well then it must undergo Inversion Testing to ensure that when completely upside down (360 degree roll) the child will be contained within the seat and not fall out.
Any claims that a carseat manufacturer makes about additional safety features and improved performance in collisions need to be taken with a grain of salt as those claims are not (unless specifically stated otherwise) tested by an independent third party. The line between legitimate claim and marketing hype can be pretty thin. I’m not saying to ignore them altogether, but rather to keep the claims in the right context.
Some people try to look at carseat safety the way they look at vehicle safety – with some doing better in crash tests than others. Unfortunately you can’t draw an adequate comparison because of the issue of user error with carseats. With cars, there is no 'user error' factor at play with the construction of the car, which is what they're testing in a crash (ie how well did this car hold up when smashed). With carseats though, clearly a carseat that wasn't installed properly isn't going to hold up as well as one perfectly installed. Kinda like condoms used perfectly are 98% effective, but condoms used typically are 90% effective. And if the carseat isn't a good fit in that particular vehicle it is unlikely to perform as well in crash testing etc.
What DO you pay for then with the higher-end seats? You’re paying for things like superior fabrics, thicker straps, a no-rethread harness, one-hand adjustable headrests, and other convenience features unique to the manufacturer. If these features make the seat easier for you to use properly then they will increase the level of safety that they provide your child – not because the seat is necessarily inherently safer but because you are able to use the seat properly with greater ease.
At this time the extended rear-facing options in Canada from least to most expensive are:
Evenflo Sureride/Titan 65
rf 24" seated height or 40” total height whichever comes LAST; 40lbs
ff 54” total height; 65lbs
Aircraft approved seat weighs 10.5lbs.
$140 but I’ve seen it on sale for $100
rf 23" seated height; 40lbs
ff 50” total height; 65 lbs
Aircraft approved seat weighs 15.8lbs
$180-$210 but I’ve seen it on sale for $150
First Years/Lamaze TrueFit Premier
rf 25" seated height; 35lbs
ff 50” total height; 65 lbs
Aircraft approved seat weighs 20lbs
$210 but this seat seems to be hard to find in Canada at the moment.
Diono Radian 100
rf 23.5" seated height OR 44” total height whichever comes FIRST; 40lbs
ff 57” total height; 65lbs – then converts to a booster up to 100lbs
Aircraft approved seat weighs 25.5lbs
** In 2014 Diono released the Olympia which has the same height stats as the R100 but the rf weight limit is 45lbs & it boosters to 110lbs.
Diono Radian RXT
rf 23.5" seated height OR 44” total height whichever comes FIRST; 45lbs
ff 57” total height; 65 lbs – then converts to a booster up to 120lbs
Aircraft approved seat weighs 26.15lbs
**In 2014 Diono released the Rainer which is similiar to the RXT except it rearfaces to 50lbs, and has head wings.
Diono also has the 2014 Pacifica which is similiar to the R120 except that it rearfaces to 50lbs.
You can compare all the Diono seats here
rf 43" total height; 50lbs.
ff 49” total height; 65 lbs
Aircraft approved seat weighs 33-38lbs.
Seated height refers to the height of your child measured from their bum to top of their head when sitting on the floor. The seats mentioned above allow the top of the child’s head to be up to 1" below the top of the hard shell of the seat (NOT the headrest and not the cover over the shell) with the exception of the Diono’s which only allow 1.5”. Each of these seats can then be turned forward-facing for continued use until the forward-facing height or weight limits are reached.
The rear-facing allowances in Canada are different than they are in the US so if you look online for seat stats make sure you are looking at a Canadian source. Also read the manual carefully as most seats which have an adjustable headrest can only use certain positions/slot heights while rear-facing in order to provide adequate safety for the head.
Rear-facing until age 2 is where you see the greatest statistical increase in safety, and is considered the minimum recommendation of car seat pros. Around age 3 the spine starts to harden in some kids, so the statistical safety increase is smaller, and by 4 most kids have solid enough bones to safely forward-face. Whenever possible carseat professionals recommend that you keep your child rear-facing in an appropriate carseat until age 4 or as close to that age as possible.
You can learn more about the value of extended rear-facing here.
References, Resources, & Recommended Further Reading
Carseats For The Littles
The Carseat Lady
Transport Canada Keep Kids Safe
MTO Safe & Secure