Greetings once again.
Well I have been hard at work investigating the two kits and have come up with the following facts. None of this stuff can be disputed. No subjective stuff, all objective stuff.
The Zvezda box is much bigger than the Trumpeter box and both boxes are very sturdy, more than adequate to protect the contents from even the most forceful postal service. 
Whats in the box?
Instructions
Zvezda                          
8 Pages                         
21 Steps                        
Trumpeter
28 Pages
41 Steps
Sprues
Zvezda
7 Sprues
Sprue A  2 parts               
Sprue B  33 parts              
Sprue C  78 parts              
Sprue D x 2  91 parts          
Sprue E  17 parts              
Sprue F  1 part                
Decals
Flag                                
Trumpeter
10 Sprues                              
3 PE Frets                          
Sprue A  29 parts
Sprue B  47 parts
Sprue C  30 parts
Sprue D x 2  102 parts
Sprue E  35 parts
Sprue F  27 parts
Sprue J  6 parts
Sprue K  2 parts
PE-A  83 parts
PE-B x 2  104 parts
PE-C  11 parts
Decals
Anchor Chain
That is what is in each of the boxes. The Zvezda kit has 313 parts whereas the Trumpeter kit has 686. In parts count the Trumpeter kit is way ahead.
The Zvezda sprues are all in separate plastic bags except the two D sprues, the only thing is that none of the bags are sealed and any part that may escape from a sprue is free to roam around the box.
Each of the Trumpeter sprues is also in a plastic bag but these are all sealed to prevent dissident parts from escaping captivity.
Dimensional Accuracy.
That is accuracy that I can accurately measure before anything is glued together, so that means basically the length of each model.
Both kits have divided their hulls in half and the only way to get a waterline model is to hack the hulls apart using knives or other cutting tools.
The original ship was 537ft long (160.6m). I work in metric so I will be using the 160.6m figure. It did not say if that was at the waterline or overall so I will assume it is overall length.
In 1/350 scale this works out to be 458.5mm long. The Zvedza hull is 456mm long and the Trumpeter hull is 461.3mm long. So the Zvezda hull is 2.5mm short and the Trumpeter hull is 2.8mm too long. Pick your poison.
These dimensions may change slightly when the hulls are assembled.

As you can see from the photo the Trumpeter hull is definitely a few mm longer than the Zvezda hull.
As you can also see from that picture both the kits have their hawse pipes open which saves you doing it yourself.

In this picture you can see the differences in the Zvezda (bottom) and Trumpeter (top) hulls. The detail on the Zveda hull is a little softer than the Trumpeter hull. 
Neither have drilled out portholes. Both have holes to locate the torpedo net booms.
You may also notice that the Zvezda plastic has like a swirl of different colour plastic through it, like a choc swirl ice-cream but using tasteless grey plastic. The Trumpeter
kit is moulded in their usual light grey, well usual for ships anyway.
One more thing for this installment, price... These are the cheapest prices I could find for each on the internet using sites I know to be honest and reliable. You may be able to get them cheaper on some super-sale but here are the lowest prices I could find.
Zvezda - $52.82 + postage
Trumpeter - $36.01 + postage (I actually bought mine from here)
So there you have it. So far it would appear that Trumpeter offers incredible value for money including PE and an anchor chain for a lower price than the Zvezda kit. 
BUT will this price advantage be enough for the Trumpeter kit to be considered the better buy? We will look more deeply into the details of both kits next time.
Same bat time, same bat channel..
Cheers
Warren 
