There's vastly more to politics than that. There's even more to "small" vs "big" government than that, or to who really promises and delivers what. This convenient reduction to handy little words obscures all that, to the point where it stops mapping to reality in a meaningful way. It's a fictional abstraction.
If anything, your question reduces to making one party sound incompetent or deceitful, I don't know if that's intended. (And considering that aspect of the party is another fun can full of real-life worms.)
Based on the parent comment, I think it's more "one party sound incompetent and the other deceitful". There was a senator who used to say that American politics was a contest between the stupid party and the evil party.
It's stupidly obvious. Politics is about how we organize government and distribute power to solve the problems of living together as a society of individuals. "Big" vs "small" government is a particular way of interpreting one aspect of that. It's an important aspect and a useful perspective, but even if taken at face value it completely neglects other important things like the rules for making policy and their actual content. Of course, the face value of big vs small has become a mask for something else.
But if you've spent the time since your teens to come to the opposite conclusion in spite of everything going on around, then I suspect there will be very little I can say to you that will make sense to you.
If anything, your question reduces to making one party sound incompetent or deceitful, I don't know if that's intended. (And considering that aspect of the party is another fun can full of real-life worms.)