I was looking through http://uesp.net/wiki/Skyrim:Trainers and I noticed that everything that the Companions can train you in, other factions or non-faction trainers can do the same thing, if not better. They have expert training in block and 1-handed, but the master training can only be done in Orc strongholds, which have nothing to do with the Companions. Heavy armor training? Join the Dawnguard, or better yet, just align yourself with the Thirsk. 2-handed training? Join the Volkihar, or better yet, help the Skaal. Smithing? Join the Dawnguard. Archery? Niruin of the Thieves Guild and Sorine of the Dawnguard do it much better.
Now, compare this with other skill trainers. The Bards College has a monopoly on speech. You must join the Thieves Guild if you want to master Sneak, Lockpicking, and/or Pickpocket. You must join the Dark Brotherhood if you want to master Light Armor and/or Alchemy. The College of Winterhold has a monopoly on Destruction, Alteration, and Illusion, and even if you learn about Conjuration (Falion and Talvas) and Restoration (Danica and Florentius) outside of the College, you must still gain admission into the College in order to take the master quests and learn the final spells. Although, yes, Neloth and Hamal outside of the College can teach enchanting much better than Sergius of the College.
Edited by MidbossVyers, 06 March 2015 - 03:06 AM.