Ash doesnt work nearly as well, its more expensive and pulls forward meaning it has to be in front of hydra, blocking him from attacking and standing right in the line of fire. Honestly ash really only seems to work with powerful one time use abilities like boss noxious or hercubees as a way to activate the ability then immediately get them out of the way of retaliation
The amount of times youd need to retreat one extra tile away from the opponent that you cant just… walk to with the 2 actions you have is a lot smaller than the amount of times you want to use a high value ability from 3 tiles away instead of 2 so that you dont die doing it
Cer costs 2 more for only 300 more attack, if youre going for any kind of heartrush build which you often are with these 1-1 juggernauts as they tend to last poorly in teamfights, hydra is much better
Im not crazy at all lol, most top players agree with me. Heck the guy who pioneered top level hydra and cerb strats thought hydra was better. Before that guy basically everyone thought they were unplayable at top level. Pre le-shovell cerb being better was out of the question, he was way worse. Post le shovell he can actually get hits in so theres a case for using him, but a lot of players still prefer hydra as a cheaper option including me. You gotta remember if you wanna heartrush you wanna go fast. And running hydra not only lets me get my stuff in faster, it also let me chain into another unit. One excellent combo if you wanna run hydra instead of cerb is going bad omen into hydra. Its a simple 2 turn combo that lets bad omen shut off the entire enemy team while hydra goes in for the heart. With cerb ive gotta funnel all resources into him and might not get the time to get the stuff i want to before they bring out repellers and stuff to counter him.
Admittedly, im far from the best hydra/cerb player. But a lot of the best hydra/cerb players tend to go for hydra over cerb cause again, the best way to play them is heartrush and hydra being two keys cheaper gives the opponent less time to set up the many counters that this kinda playstyle has to deal with