What is better?
You might wonder now what technique is better. To be honest, I haven’t figured that out myself yet 
But I can explain you the benefits and draw backs of each:
Technique 1
Benefits
- It’s faster and easier to set up.
Unwrapping is kept to an absolute minimum and requires little skill. You just have to be careful with areas that “fold back on itself” such as airscoops. Also, if you have engine nacelles you may have to break them off and map them on a different location in your UV layout. In the case above, you notice that the wing overlaps the rear fuselage. This is wrong of course, and in a later stage the wing was detached in UV1 and moved into one corner so it wouldn’t receive the fuselage mapping. But that’s about all unwrapping you will have to do. Other than that it’s simple planar mapping.
- You can keep the textures smaller.
Since you’re using MAX materials anyway, texture resolution doesn’t matter and you can optimise the textures to the shape of your model. This way you can keep each texture relatively small compared to when you would unwrap the entire model on one sheet. Smaller textures are of course much more pleasant to edit in Photoshop.
- Seamlessly easy.
By having waved, blurry or speckly edges on your mask, you can prevent seams on your texture really easily. Top/bottom and side views will blend in perfectly and make a neat skin for your mesh. If you keep the length of your top/bottom and side view textures equal, it’s also really easy to match up panel lines and such. Also you can generate your right view from your left vuew, and your bottom view will have a lot in common with your top view. So creating your textures is quite a bit easier too.
Draw backs
- You can end up with many textures.
In case of a very complcated model, you can end up with many textures. In case of my Mustang, I wanted a high texture resolution, but not the burden of big textures. So I split up my model in quite a few (too many!) different textures:
fuselage_top
fuselage_left
fuselage_right
fuselage_bottom
wing_top
wing_bottom
wing_front
tailplane_top
tailplane_bottom
tailplane_front
…and of each one a diffuse, specular and bump variant. As you can understand, the material structure got kinda complicated in the end, with lots of Composite and Mix Maps.
With the example above I was able to keep it much simpler. Top, bottom, left, right (which I never bothered making in the end! :D).
Many textures can be a pain when you want to change something, such as the positioning of a marking that goes across the fuselage. This can easily mean you have to edit 12 textures to adjust one item on it.
- Materials can get complicated.
As mentioned above, material structures can get a bit complicated this way. This also means that MAX has a harder time calculating the materials, which can make rendertimes longer.
Technique 2
Benefits
- Simpler materials.
If you manage to map everything onto one page, it’s really easy to set up your material. All you need it one Bitmap and no hassle with Mix Maps and Composite Maps. This also improves rendertimes.
- Fewer textures to edit.
If you manage to unwrap everything to one texture, you will have an absolute minimum of textures to edit. Quite convenient when you want to make many variations of your model (different camouflages etc…).
- Stretchless.
You can unwrap your model in such a way, that there’s no noticeable stretching. With Technique 1 stretching will be limited too, however, never exceeding 45 degrees if you do it properly.
- Trouble-free export & real-time use.
Having unwrapped your model properly means that applications that don’t support MAX materials can still display your model properly. So you can export your model to a different application and the materials will be preserved. This will allow your model to be exported to Shockwave 3D, for example, so you can view it in real-time 3D. There are several examples of this on my website.
Draw backs
- Tricky to set up.
For many the unwrapping process is a complicated one, and for all it’s elaborate. It simply takes time to align everything the way you want it. And mistakes are easily made if you lose track of where everything goes. It’s also more complicated to edit the texture once it’s unwrapped, as all parts have to meet up in the end. This brings us to…
- Seams!
Breaking up your model creates countless seams which have to be cleverly edited on your texture in order to not show up. Here texture baking can be a great help. Imagine having a Tiger Meet F-16 to texture… matching up all the tiger stripes with this technique can be a nightmare. The best option is to make a new, planar, mapping set for this (UV2) and bake it to your unwrapped texture (UV1). But this is a completely different story altogether! 
- Big texture size!
For me, the main problem with this technique is the huge texture sizes required to keep a decent resolution for your model (if you unwrap to one single texture). Anything over 2048x2048 will really make Photoshop choke, and the mentioned resolution is rarely sufficient for. A sulution to this is to scale down unimportant parts and thus free up space for more important parts. For example the bottom of a tailplane will rarely be viewed up-close and can be scaled down, allowing the textures of the nose to be bigger to add detail which will show in close ups. But having parts a different scale also brings trouble: seams will be harder to hide and panel line thickness will vary, which might become noticeable if you’re not careful.
In general I seem to be using these two techniques in alternating fashion! No kidding!
Once I’ve done a proper unwrap I’ve become frustrated with the large texture sizes and poor texture resolution. So I switch back to the quick&easy method. But then I get annoyed by the many different textures I need to edit in order to make changes. Not very pleasant when having to do many different variations. I’ve used the quick&easy technique on my Mustang and now regret it as I’m planning to do many versions of it and editing the textures and materials is becoming a bit chaotic, as there are so many of them! So next model I’ll probably unwrap properly again!
However there is no reason to stick to one technique. In fact, I seem to have found that combining both techniques works well too. One of my current models uses both mixmaps, but also is unwrapped semi-properly. This way I’ve managed to keep both texture sizes and quantities to decent levels without sacrificing quality. The best of both, so to say. But it also means the worst of both. The material setup is not suited for export, for example, and I still had to make the effort of unwrapping the model and dealing with seams.
The ideal solution? I guess that depends on your personal wishes. If I had a superfast computer that could deal with 10,000x10,000 textures easily in Photoshop, I would use Technique 2 exclusively. But since that is not the case, I’ll likely keep alternating these techniques on a per-project basis! 
Well, I hope this “mini-guide” was of some use to those of you who struggle with texture mapping aircraft! Any questions, shoot! 
Excellent tutorial! A big thanks for your efforts.
