I happen to have them all (and more)...
The Maerklin 36851, 36857 (Version with RAG markings) and 36606 are all Maerklin Hobby models and have rather basic motor and decoders although having metal bodies and limited details. 36851 and 36857 are loks from the first series. 36606 represents a lok from the second series.
The Roco 69591, 69592, 69599, 69501, 68506 are all more detailed models, OEM ESU decoders and good motors, albeit with plastic bodies. 68501 is a Re 484 for Italy and Switzerland. 68506 is a Re 482 from the second batch.
There is also Trix 22631, which is similar to Roco 68506 in quality and detail, also having a plastic body, but would require conversion for AC operation.
The first three Roco models are older productions, and still have bulbs for the head- and taillights. The last two models have LED lighting.
The Maerklin models all have yellow LED lighting, with no taillights.
I will take some photos and attach them to this post, so you can see the details.

You can see the detail is of a much higher level on the Trix model (front) than the Maerklin model of the same lok (rear).

Trix (DC) in the front, Maerklin in the rear

Maerklin's 36851 (482 011) vs 36606 (482 046)

Roco's 69592 (482 002) vs Maerklin 36851 (482 011)

Roco's 68506 (482 039) vs Maerklin 36606 (482 046)

and finally... Roco's 69592 (482 002) vs 68506 (482 039):

The Trix and Roco models both have a much higher level of detail than the Maerklin version. This includes pantographs and other roof details (multicolored), bogie and wheel details, integrated close coupling mechanism. The first Roco models had light bulbs. The newer ones have LEDs/
More info on the prototype and the differences in real life can be found here:
Traxx AC 1 (482 000-034):
http://www.railcolor.net...p?nav=1405291&lang=1Traxx AC 2 (482 035-049):http://www.railcolor.net/index.php?nav=1405188&lang=1
Regards
Mike C
Edited by user 20 January 2012 07:52:03(UTC)
| Reason: Not specified