It depends. I took Schweser for levels 1 and 2 and barely opened the core materials.
For level 3 I took Chalk & Board and it blew me away how much better it was than Schweser. On levels 1 and 2 I got in the top results for test takers, but I never felt fully confident until I got my exam scores back. On level 3, I knew in my heart I did well on it immediately upon completion. I attribute this entirely to Chalk & Board and Nathan’s way of explaining topics in layman’s terms - and also Schweser has short cuts built into it that I wasn’t fully aware of before.
If I had to do it all over again I would take Chalk & Board for all 3 levels, skip Schweser for their exam prep and just buy the Schweser mock exams separately which is pretty cheap. Other folks who have taken other providers may be able to speak to them. A good prep provider will not only teach you to pass the test but will also teach you the nuances and logic behind questions. Schweser doesn’t do that but Chalk & Board does in my opinion, and probably other services do too. Meldrum, LevelUp and Bill Campbell for example offer services that I haven’t taken personally but they seem to get great reviews.
If you have the stomache to read all the CFA core curriculum materials then of course that’s the clearest way. But I needed some help typically. I used the Chalk & Board videos on level 3 and took 120 pages of notes off of them, broken into topic sections. Those notes became my study book, and if I needed further clarification I looked at the core curriculum materials.
Cheers - good luck - you got this👍