Giles by far, but maybe I can't quite articulate why. I love both of them. But to me, Giles has way more depth and texture as a character.
They are both unbelievably courageous, kind, loyal, and devoted to the mission. And VERY good looking. 🙂 With good senses of humor. And an endearing bumbling manner at times. And an ability to be bad-ass.
Both of them looked endearingly foolish at times - Wesley in the early seasons of AtS and Giles when (for example) he was practicing his pickup lines to an empty chair, and being caught doing a solo swordfight in the library.
It really can't come down to which one is a better man -- they're both outstanding men, and for almost exactly the same reasons.
So it has to come down to which one has more depth and texture as a character.
We know that Giles's father disappointed him by telling him he had to be a watcher rather than a grocer or a fighter pilot; and we know that Wesley's father emotionally abused him terribly -- but other than that, we know nothing of Wesley's past, while we know quite a bit more of Giles' past and it plays a role in the show.
We've seen Giles interact with other faculty, with Scoobie friends and family, with Spike, with other Watchers (Gwendolyn Price and Wesley), with the Council, with customers at the Magic Shop, and with authorities (many times). Wesley's interaction with people other than the main characters was much more limited, so we didn't get that kind of glimpse into his character.
They were both tortured, but Giles's character was allowed to react in a defiant fashion ("in a tutu ... pillock"), which gave his character more depth.
They both lost loved ones to murder, but Giles' reaction was much more dramatic.
The entire foundation of Giles's role in the BtVS series was a beautiful, well-developed father-daughter relationship with his Slayer. Wesley had nothing to compare to that.
As part of this relationship, Giles helped Buffy through the death of her mother, someone he had had a brief physical, and then a friendly, relationship with. We saw no parallel for Wesley.
Giles experienced the death of his Slayer, and we saw the emotional fall out from that, including the bittersweet scene where he is treating robo-Buffy as if she were the real Buffy -- and the epic scene where he is reunited with the newly-revived Buffy.
We got to see Giles sing. 🙂 (And not bad karaoke.)
We got many intimate glimpses of Giles's home, and his jobs other than Watcher (librarian, magic shop owner), while the few glimpses we got of Wesley's home were sterile and unrevealing, and he had no other job.
We got to see Giles drunk twice, and hungover once. We got to see Giles as a demon.
Perhaps one of the most interesting distinctions is we got to see what presumably normal character (i.e., not a villain or demon) Giles hated -- Professor Walsh.
And here's another interesting, two-part, difference. Giles made more mistakes (which made him more human and added to the texture of his character), and acknowledged when he made mistakes, which Wesley did not. Giles apologized to Buffy for his role in the Cruciamentium. Giles acknowledged his error in "Doomed," when he had the Word of Valios and didn't realize it. Giles (not in so many words) apologized for his role in the misunderstanding of The Yoko Factor. He came around in the finale of season 1 when he decided he would face the Master, and in the episode where he acknowledged he was driving Buffy too hard. He apologized in Grave for leaving Buffy. Wesley never acknowledged that he should have talked to Angel and the others about the prophecy instead of kidnapping Connor.
Giles killed a human being for the good of the mission. (Wesley chained a woman in his closet, but that's not quite as bad-ass.) Giles told his daughter-figure to kill her sister.
Giles had a fight practically to the death with someone he had clearly loved (Willow).
We got to see Giles experience angst about his aging, and his relationship to the Scoobies, and about his not having a job ("Alfred had a job.").
Giles went through the angst of deciding to leave Buffy behind in season 6.
Giles had better sarcasm.
In a way, this is really just a poll about which character was better or more deeply written. The argument that Giles was irrelevant after season 5 is just an offshoot of the fact that Anthony Stewart Head wanted to return to England to be with his growing daughters, not a reflection on the Giles character. Otherwise the characters are very similar in their traits. But the fact is that Giles was better written, and more deeply written, throughout the series.
If I had to say which one I'd rather have a beer with, though, it would probably be Wesley. 🙂
