What it basically comes down to is personal taste and opinion. There's no evidence to support that the 1989 Batman film is better than The Dark Knight just like there isn't evidence to support that The Dark Knight is better than 1989 Batman.
The way I see it if there's still this solid debate over which film is stronger, a few years later they must both be pretty damn good.
In Batman's defense, it has some years under it's belt. 21 to be exact. The Dark Knight has a mere 2. I'm not saying that The Dark Knight won't hold it's own for years to come (I know it will), but we're getting to an over saturation point, mostly due to online activity I think.
What could take years, perhaps even decades to discuss, like plot points, psychology, etc. has pretty much been summed up these last couple of years. Analysis and enjoyment of Batman have been taking place for two decades.
Don't some of you want to "rediscover" The Dark Knight a few years from now? It's a great feeling, going back to "old times" and catching up on things, while you still love, haven't been very prominent in your views or hobby.
Anyway. There's merit to be had in both films, but unfortunately some sides won't see it that way. I never seem to see any happy medium. It's always one, or the other.
I'll never choose, but with this Hot Toys announcement I'm in total 1989 Batman mode. The Dark Knight has had plenty of time in the spotlight, from discussions to collecting to appreciation. God knows from 2006 to, man maybe, this year I ate, ____, and slept The Dark Knight. I think it's safe to say I can cross over enjoy an old favorite for awhile.
It's nice to have variety, I think. Choosing one over the other is a bit boring.