When you have a sexy voice like Troy Baker, you can voice every character in a game for all I care. 
Plus, we need an experienced voice for the protagonist, otherwise, we have Fallout 4 male protagonist that sounds like a bored white guy half the time. He can't control his emotions and jump all over the place. That was his first gig. i would rather have someone with a bit of experience to voice the protagonists.
Brian T Delaney has been in loads of games but I don't know that he ever voiced a playable character before. Regardless, I think he did a fine job in FO4. He had a good range of emotions which I'm beginning to realise is probably my number one personal requirement. I don't care how cool or sexy a voice sounds if the acting is like a talking plank of wood. Mark Meer's acting got so good in ME3 that it makes it hard to go back to ME1 or play another game where the PC talks with all the emotion of a carrot. There are 16 voice actors for the 8 different classes in SWTOR and while none of them are awful, some of them seem really bad compared to the stand-out stars that make the characters come alive.
Back on topic. I like FPJ and I really liked Vega. Everyone hates him but he was like my Shep's bro (I never use that word) and I never got all the Garrus love. My favourite, non-romance squadmates were probably Ashley, Miranda, Thane, Samara, James and Edi. I never really got attached to most of the "core" cast. Tali got about as much action as the hamster.
I didn't really like Bull or the voice Freddie did for him but I got used to it over time. If he comes back, then I'd rather he just use his normal speaking voice.