I think archmage's charm
is to UW control what esper charm
is to esper control, and similarly for generous gift
and kaya's guile
UW control for the last two years or so has been kinda chunky and heavily reliant on planeswalkers and "removable" answers to noncreature, nonland permanents. It had a few key problems: inability to answer noncreature, nonland permanents cleanly, inability to efficiently answer threats presented in a "tempo oriented" fashion, and no way to cover those bases without stretching the permission so thin that the archetype didn't just devolve into a midrange deck. What it's very good at is punishing overextended creature boards, repeated unprotected threats, and preventing an opponent from ever turning a game around once they're on the back foot.
Esper, without esper charm, has a powerful and robust suite of answers but had a shocking vulnerability to blood moon, the same card draw problem, and difficulty with decks that attempt to leverage mana efficiency in a single turn to generate substantial advantages.
For UW, archmage's charm fills that hole--it's a clean card drawing spell, which is kind of a fundamental requirement for any sort of weissman style control build. It has the flexibility to protect walkers from aggression by stealing blockers and it has the counterspell mode for matchups where playing to the board is unimportant.
For Esper, esper charm fills those holes--it's again a clean card drawing spell, it provides insurance against blood moon, and it allows the esper deck to pressure decks looking to leverage single-turn actions (like ad nauseam or tron) by taking away their ability to stockpile resources.
Similarly for gift and guile, they fix problems. UW had trouble closing games but also dealing with cards like karn, ensnaring bridge, lattice, etc. Esper had trouble answering graveyard value engines. Those cards fix those problems. The end of turn gift-snap-gift, untap and colonnade activation ->swing for 12 is a real thing. you flash in a clique, you hit once, pass, then execute this sequence when they do nothing, and the game is over.
While I don't think you're wrong to play esper over UW specifically because of hogaak, I think people aren't looking the one level deeper at the metagame: Jund and Urza Thopter-Sword are both powerful archetypes kinda hidden beneath the surface, alongside izzet phoenix and red prowess. I think it's pretty clear that UW has the better matchup against the first two because of Rest in Peace, I think izzet phoenix is such a good matchup for both decks that it may as well be a wash, and I think esper is strongly favored over UW when it comes to red prowess (Hello Kaya's Guile!). For myself, I don't think it's worth trying to salvage the hogaak matchup--you'll play whatever grave hate you play, maybe increase quantity a little bit, and move on with your life. Because of that, I look at the metagame and see signs that tell me I want access to Rest in Peace, not surgicals or kaya's guile--it's just substantially better against Jund and Urza thopter-sword. I also think the tron matchup is slightly favored for esper vs my builds of UW, and significantly favored vs typical builds of UW, but I don't see tron as being a big enough player at the moment to weight heavily in my decisionmaking.
When hogaak goes away, we'll see the metagame settle a bit, and I think it's likely I move back to esper as Jund and Urza come up against more prepared fields.