I bought the bundle and tested on practice map and both are very effective at taking down planes.
I then put both in my BR4 presets, the Skink is very effective against jets a short burst and saw my killfeed.
The Skink is a nice AA plane defence, people say overheating and magazine size an issue. I would say its ok but it takes trigger discipline not just down hold fire. Skink can damage enemy armour. But it’s purpose is planes and not frontal assaults.
Kubeblitz has nice cannons and felt more effective as an assault vehicle unlike the Skink. The armour seems more effective, maybe lower profile harder to hit?
No regrets with either AA tank, nothing more satisfying putting down a 262, Ju188 or swatting a Meteor F80 out the sky. They will be part of my permanent lineups.