Joss said that he wasn't sure about DB at the audition, but the women all said he wasPattinson is certainly a more appealing and talented actor to play the male lead than, oh, David Boreanaz (who isn't?). That said, I prefer James Marsters.
I was never terribly impressed with Boreanaz's acting when playing Angel. He just doesn't do angsty, guilt-ridden, layered characters well at all. Probably due to the fact that he's actually a pretty funny and charming guy in real life. It felt like he was cast for one reason - his looks, or at the very least his hair.
and that they should hire him, even though Joss was like: "Really? But he has a forehead thing going on" 
Indeed, DB is a very attractive guy, but I wouldn't call him classically handsome.Judging by that story, they were mostly choosing an actor based on attractiveness - which makes sense since Angel wasn't supposed to be on a show for long. He was a guest star in season 1 and probably wasn't meant to return. Who knows how things would have turned out if they had cast another actor, even if his acting had been better than DB's was at the beginning. They kept him on the show and developed him because he had pretty good chemistry with SMG, the character was popular and people liked the B/A relationship.
Allegedly, later on Joss thought that David's acting had gotten really good and that he could carry a spinoff. Though I'm sure it was also because a) the character was really popular and b) they didn't know what to do with him on BtVS anymore, which was painfully obvious in season 3. They seemed to be preparing him for a spinoff in episodes like Amends.
I liked his acting on AtS, and I think his personality might have helped to make Angel different from your typical broody tortured character, and give him a goofy side. I like the way SGX describe him in their 25 SF/F icons of 21st century article:
Because make no mistake. Angel was the eternal teenager. His new role as head of Angel Investigations may have made him feel all big and grown-up, but he still brooded and pouted like some pubescent boy. Somehow, that just made him all the more likeable, especially his hurt expressions when his colleagues took the mickey out of him for it.
Angel could have been a very one-dimensional character (like Edward and Stefan) but Whedon and Boreanaz between them created a character with a self-deprecating humour, tragic depths, petulant flaws and, underpinning it all, a desperate, almost monomaniacal urge to do the right thing. But he really couldn’t sing.
