Looking at this from an EU perspective here.
The Imperial Star Destroyer and the reason being? It's simply the superior ship across the board apart from fighter compliment. But that's just 1 point vs a dozen others. I can be out longer with an ISD-2 before refueling/restocking supplies, can take far more damage and still go on.
I can conduct both space operations and planetary operations out of an ISD. A Venator can really only do space, as it's not exactly optimized for ground operations. That's why they had Acclamators, those were the ships that were optimized for full ground operations.
I have repair/recovery vehicles in an ISD, so should after a battle there needs to be a pickup, won't be a hassle.
There's also the issue of, the Venator basically has to work with other ships otherwise...it's pretty screwed on its own. It lacks the means to do long range operations.
So yeah, the ISD-2 is just far and away the superior ship apart from fighter compliment, but that's 1 point vs a dozen others in favor of the ISD. Even the greater fighter compliment has actual downsides, so the advantage is also a slight negative, given you're also going to need a ton of resources to keep those ships going.