This is about Long War for the first game, I haven't played the XCOM 2 yet.
Long War is… very different. It's hard, but for me, it was mainly about having to shift the gears from old mechanics to something new.
- You need to maintain a large roster of fairly evenly trained troops, as there is fatigue on top of longer recuperation time. Seriously, you want to have about thirty mid-tier troops over a dream kill team of officer specialists.
- Research requires more time, so you might find yourself still fighting with laser weapons sixteen months into an invasion. IMO it's enough for end-game, but your mileage may vary.
- Deployed squad size is larger, but your opponents have better cooperation procedures.
- Panic isn't as erratic when it comes to changes. Everything you build, from satellites to interceptor bays, will have an effect on it. Same goes for its destruction.
- Many more little tweaks like that, I can go on if you want.
It's hard, but I don't know if I would compare it in a 1 to 1 relation. You need to take your time, both in-game and out. It's a Long War after all. Also, Wiki is a frigging lifesaver!
If you like quality Let's Play videos, I can recommend Beaglerush's series on Long War.