Flax and canola really aren’t comparable. Omega 3 and omega 6 are essential nutrients. Canola is mostly omega 9 (~60%)(which you need, but your body can manufacture from 6s or 3s). It also contains linoleic acid, a bioavailable omega 6 (~20%), and a small amount of ALA, an omega 3.
Flax oil (Wikipedia is for" linseed oil") is mostly ALA. So people often describe it as a good dietary source of omega 3s. The problem is that ALA is not directly useable in mammals. Instead we need two other omega 3s: DHA and EPA. ALA first has to be converted to a form that can be used. ALA --> EPA --> DHA. Unfortunately, humans aren’t very good at converting ALA to EPA, and we’re even worse at converting EPA to DHA. The conversion rates of course vary depending on the availability of the resources needed for the conversion, but I’ve heard estimates ranging from something like 1000:1 to 20:1 ALA to EPA. I have also never been clear on whether it is actually possible to manufacture enough EPA/DHA from ALA to meet nutritional requirements, but that may just be my ignorance. Just to give you an idea of how important this stuff is, Wikipedia describes DHA as a primary structural component of the brain, skin, sperm, and testicles, among other things.
I’ll also say that I’m not a huge fan of getting these short-chain fatty acids in liquid oil form. They all oxidize (i.e. go rancid) quite readily, particularly in the presence of heat. That’s why the “cold-pressed” aspect is important. In most industrial extraction, with uncontrolled heat, a lot of the short-chain fatty acids are basically rancid before they get into the bottle, and then it doesn’t take too much time on the shelf for them to go the rest of the way. That’s actually why flax oil is usually refrigerated. Unlike canola or olive oil, oxidated flax oil actually turns into a solid polymer. That’s why linseed oil (same thing as flax) is used in paints and wood polish.