Unpopular take on Howling Abyss
I'm with the crowd of "BoP has been a breath of fresh air for the mode". Not saying that is either map is better, I'm saying, there are things in BoP like the alley made more interesting plays possible.
I have over 9k games in ARAM so I think I have some legitimacy in the debate.
The Howling Abyss has less vision to control ( less gaps to close unseen as melees => harder games for a melee ) and also, vision control is a good thing to have, it creates fighting and skirmishes which is not in favor of uninteractive comps. I ff'ed an even game just because both teams were afk. Nothing to fight for. Vision in BoP would have been the thing to fight for. You guessed it I'm a big fan of the alley they added.
Also wider map on BoP allows for smaller skirmishes to happen without having 5 man collapse on you. For champs that have no disengage tools in their kit, it can be irritating and suffocating if enemy has a counter to you when you step up. Its okay to have an enemy Poppy, its not okay to have an enemy Poppy almost always in range to wallstun you when you're a wall abuser.
Other than that, the rest is to be thrown away(the added bushes, maybe reposition them? I don't know, no symmetry creates unecessary imbalance; speedboosts, inhib buffs).
Maybe I haven't gotten fully used back to HA yet, but thats my take for now. Definitely having a tad less fun than 2 weeks ago in ARAM.
Happy ARAMing!