Flax covers many bases but I am not a huge fan. I completely recommend it in small servings though... many benefits.
Although you should know as it takes up space in your small intestine, it can block the absorption of certain medications. Flaxseed also increases the intensity of blood thinners and blood sugar medicines. It is mainly made up of ALA. This to be is not very useful especially when you look at the levels of EPA and DHA in fish oil. Flax contains tiny quantities of both those fatty acids. They have been proven to be responsible for amost all of the omega 3 health benefits. ALA has to converted in the digestive system to EPA and DHA and that conversion is less than 1%.
Flax can make cholesterol-lowering medication more effective... I guess that is a benefit in some ways (depends on low you want it).
I would just get fish oil or neptune krill oil if money isn't an object.
For cooking I would use coconut oil.
For dressings I would use olive oil.
Out of the two you mention abit of both... but olive is a fav of mine. I use alot of olive oil.