Let's have a discussion on our views on each companions. I see that our companions have a mixed fanbase, one more than others. So, let's discuss each one. Be warned that there are SPOILERS for those that may not have gone that far.
SPOILERS down below
The first party member we meet is Lae'zel who is the only warrior of the group. Lae'zel is a character that is NOT afraid of speaking her mind and has a very strong personality. She knows what she wants. Some may not like that and other have no problem. I personally like Lae'zel because she a B**ch but more because she seems to be the most honest, even if she does keep certain things for herself. Also, Lae'zel seems to be doing things for her Queen's approval. She wants to be the best for her Queen. I think Lae'zel could end up being a loyal companion.
The second party member is Shadowheart , a cleric. I also like Shadowheart as there is a level of mystery surrounding her and her devotion of the Goddess Shar. I see Shadowheart being the MC's best friend as long as you have her approval and you don't romance her. She tells you from the very beginning if you save her that she owes you and will repay you when the time comes for saving her. She also gives you advice and is always telling you to be careful. That tells me she sees you as friend and care about you. As for her mystery, her artifact plays a big role. Such as, what is it? Where did it come from? Why was she sent to steal it? Why does it protect you when you go to the Goblin camp? Why does the Githyanki want it? Her character and her backstory is very interesting.
The third party member is Astarion, the only rogue of the group. The BIGGEST love and hate relationship the players have with him. I personally love Astarion and feel he is the most misunderstood of the group and the most emotionally damaged. Which is why I feel for him because a lot of the things he went through were not his choice. He's a slave who has been tortured by a Vampire Lord named Cazador. If people choose to keep Astarion in the group and often talk to him, you will learn a lot from him. Approval has to be high. If you have Astarion's approval he will tell you that he doesn't mind staying with you when everything with the tadpole is over. He likes you. I also feel that Larian Studios favors Astarion as he is the only one that requires you to do more for his approval and he has his own romance song. I know some people here in this forum, don't like Astarion's personality but if you know anything about vampire, that's exactly how they are. Extremely sassy but if you gain a vampire's approval or even love, they will do anything for you at least in vampire lore. Dracula being the most famous.
The fourth party memeber is Gale, a wizard. I have mixed feelings on Gale especially when I first met him. When he says that he saw you lying on a puddle of blood with a tadpole nibbling on you ear. I was like, "Wait a minute, if you saw me, why didn't you try to help me?" I found that weird. There is something off about him. He does seem to be a good friend but he does have selfish motivations. You learn that he wants to be the most powerful wizard. He has a magical, ticking time bomb in his chest all for the love of a Goddess. That's a selfish motivation. It could be possible that Gale would end up doing things for power so that he can be the best wizard. He seems to be power hungry.
The last party member is Wyll, a warlock. I'm not to keen on Wyll, just like Gale, he has a selfish motivation. He wants popularity and fame. He's a glory hound. The only reason why he is a warlock is because of his pact with a demon. He basically signed his soul to the devil just for fortune and glory. Although he seems to regret it, doesn't seem that way sometimes. He wants the "Blade of Frontiers" to have a fan base.
To me Gale and Wyll are the least likely to be loyal because they have the most selfish desires. Whereas; Lae'zel, Shadowheart and even Astarion are more loyal because they have the least selfish desires.