It comes down to preference and to an extent aesthetics - I love the look of a glassy surface on a pan, but performance-wise I honestly don't think there is an appreciable difference. The good thing is no one is wrong!
I use De Buyer carbon steel pans when I need a superb sear and also to be able to take temperatures up and down quickly. It's what I used in restaurants for years (or similar from other brands) and they are lighter and generally far superior for that kind of work, but for home I just love cast iron for most things.
European 'iron' pans are VERY underappreciated in the USA. Classic cast iron is often overlooked by all but the few who grew up on farms or have fond memories of cooking with 'grandma'.
I 'rediscovered' the joys of cooking in cast iron when I was in college and had nothing but a very weak electric coil stove to cook with. $8 for a Lodge skillet and a 30 minute preheat let me cook breakfast sausage properly and my eggs didn't stick either.
Later, when I graduated and moved into apartments, I learned to really cook more than what I could I microwave or reheat in a skillet. Pot roasts and similar things were basically pretty bland even when covered in spice because the ~3# roast wasn't browning properly and was basically being steamed. DUTCH OVEN to the rescue! Room temperature after a good salting, and a 30~60 minute preheat and, WOW! Then I nicely seared and browned pot roasts, added some potatoes, carrots, etc. and back in the oven. What a difference! All from a $20 ~5qt Dutch Oven!
I was still a slow learner with Teflon skillets for eggs. ~$30 and a couple months later, another $30 and on and on it went until ... I discovered De Buyer 'crepe' pans. Those things were only ~$20 at the time and did they ever work well! Pancakes, cheese toasts, etc. were also easier to make with its low sides.
If you like cast iron, you will like French and Belgian 'elemental iron' pans, also referred to as 'black pans' by some. They cook a lot like cast iron but weigh a lot less. If you have a strong stove/cooktop, they will sear as well as cast iron but, with their reduced mass you don't store as much energy for a good sear on a weak stove.
Regarding seasoning, flax oil never worked well for me because while super hard, it tended to flake off. Most oils work well but, watch out for lower smoke point oils so you don't smoke out your kitchen. In the end, Peanut oil became my preferred oil for seasoning but, Crisco works really well too. In a pinch, any kitchen oil (vegetable) or grease (bacon, sausage, etc.) will work.
As for cleaning, unless you need to scrape build up off, ~500F sterilizes your pan so soap really isn't needed. A bit of coarse salt and a scrubbie pad is all I generally need to keep my pans clean.