That´s a really interesting poll, Brickster!
I only own 4512 (actually my son does

), but I have to admit I voted for 7898.
And that mainly for the reasons, Brickster already pointed out:
TheBrickster, on Jul 19 2009, 08:50 PM, said:
While I like the 9V system much better than the Cargo Train Deluxe R/C system, I really like the rolling stock that comes with 7898. Having both sets, 7898 has a huge "play value" with its accessories and extras.
The great accessories made me buy the blue truck, the forklift and the cargo (packed in their own polybags!) off ebay.
I wasn´t sure about the RC-trains at that time and still I am. Having built my
first RC-trainsome days ago (I got the chassis on last years event in Günzburg and bought the controller at Bricklink´s) I love the sound of the motor - sounding like a tram

, but I don´t like the idea of being captured to waste batteries on it. The horn, well we´ve read enough about it...
Klaus-Dieter, on Jul 19 2009, 10:13 PM, said:
Cons:
-gold pieces - since when is gold transported with the train?!

This is no "Con" - it´s a "Pro"!
These chrome gold tiles are so rare, I´m glad they were included to this set.
Quote
-diesel engine

- goes imo with a cargo train much better than an electric engine
...
-electric engine for a cargo train

I agree with you: The diesel engine fits better to a cargo train,
BUT I like the 7898 engine better. Great parts to MOC with. Maybe ... some day ... I´ll get it.
Siegfried, on Jul 20 2009, 02:32 AM, said:
(I loved the horn too. I hid the remote in my pocket one time when I was playing Monopoly and pressed the button whenever someone landed on a railroad!

)
Well, okay - I won´t comment.