Sketchup vs. 3DSMax
Yes it is true that 3DS is better geared toward game asset creation, but not because sketchup isn't capable, it is more a case of the design of 3DS evolving to directly support this function. 3DS has a multitude of features specifically for game asset creation that streamline the process. However it is generally much more difficult to learn 3DS and become proficient in its use enough to produce game quality models.
Sketchup on the other hand is ultra simple to jump right in and begin modeling and produce OK results. Sketchup is built around solid modeling concept for architectural design. The software has grown considerably in power and capability over its life and in many ways rivals or even surpasses other 3D modeling software. Because of its ease of use, the design of the software will do a lot of the operations required to produce a useful model for you, automatically, which is great benefit, but it also has a huge pitfall.
As stated above, if you are not careful you will make models with very excessive polygon count, simply because the program lets you do pretty much what ever you wish to and auto corrects for your "mistakes" in design. This is not to say that you will not produce spectacular looking models, just that they will not be game engine friendly, without being aware of what the software is doing for you, to make the process so easy.
I have made many models in sketchup and 3DS and yes there are certain features to 3DS that are appealing for creating game models, but in the end it comes down to the designer, more than the software being used.
With good technique, sketchup will work fine for creating pretty much anything you can imagine for use in a game.
If you find your polygon count is still too excessive, there is other software out there to help you optimize your final model, such as mesh lab.
What it really comes down to is time and cost effectiveness of whatever it is you choose to use. 3DS or blender will have a large learning curve but it will be worth it to learn how to use these programs, if you have the time to invest in the learning curve.
Sketchup will do what ever you want it to do with regard to solid modeling but you must be aware of what it is doing to your models and deal with it appropriately.
Which approach is "best" ? .....well that is up to the user. As with any design software, if the designer is using poor technique, the software wont really make much difference, as even 3DS can produce some really bad modeling examples.
I have only recently began using sketchup ( a few months now) just to see what I can do with it and so far I am impressed with it.
I have a friend who is a die hard 3DS user and insists you cant make great game models in sketchup and its only suited for rough design concept. I am attempting to prove him wrong by using sketchup to create a good quality usable X-Wing star fighter game model from a 2D top down photo of a schematic.
We'll see how this goes.
I would recommend you pick a product, study it well and learn how to use it efficiently for our purpose, which is game asset modeling. In the end if you can master a particular piece of design software, no matter what it is, you will be able to make great models. Sketchup just happens to be one of the easiest packages out there to learn. And the price is right.....FREE