Seriously just bought both and I am personally not a designer, drawer, etc. so my feedback would simply come from an average user.

Even I am just an average non-professional, office worker, I do feel much better after switching from the Star G640 to the Intuos. It is much smoother when you swipe the pen and I guess it is not only the sensitivity but also how they coated the new product line.

XP-Pen DECO 02 graphics drawing tablet :

https://www.xp-pen.com/goods/show/id/324.html

Good: the pen is quite bigger than the one from Star G640, and I love it! The new pen is too small and I can’t hold it firmly enough. I guess this is just a matter of personal taste, but seriously, I bought the DECO 02 also not to compare, but because the pen feel so good and fits so well to my big fingers. Also, I love it in the beginning because it is quite much bigger than the Star G640 . I felt like I have more room to span.
Average: the scrolling ring… have fun, don’t expect any good. It has a little light surrounding it so…the look is quite entertaining to the eyes. The tablet doesn’t have the dots for you to estimate.

It is much much more useful with the ring on DECO 02 or even the pan/scroll on the pen to me (as an office worker, sometimes, vectors editor on Adobe Illustrator).

XP-Pen Star G640 OSU Pen Tablet:

https://www.xp-pen.com/goods/show/id/250.html

Awesome: now, in the beginning, I guess it is too small, not enough roomy. However, because it has same sensitivity, only one tiny move give a long run on the screen. I have 02–03 monitors so this is such a plus. I don’t have to move my arms much to get travel between windows. This is completely what I didn’t expected. The DECO 02 is bigger but you have to move your arms quite much comparing to Star G640 .

The Star G640 is better for game osu, if you feel like you're going to invest a couple hundred hours into osu, then a XP-Pen G640 tablet might be what you want just for comfortability in the long run.

My XP-Pen G640 is going on 2.5 years and it's doing fine and I have around 25k playcount.

XP-Pen G640 is made for users who want to "try" the tablet experience, and dabble in digital painting or drawing on rare occasions.

DECO 02 has a much more professional feel and and greater sensitivity. G640 is a great consumer product, while Intuos really feels like a high end professional tool. With Star G640 tablets the pen must be held closer to the tablet to be recognized. DECO 02 is more powerful and allows the pen to be held at a great distance, in addition to its extra pressure sensitivity and express keys.

As a designer, I would not be able to feel comfortable using a Star G640 . It does feel closer to a toy accessory than a professional tool. The difference in drawing surface size, pressure sensitivity, materials used, and distance of pen recognition really do make a difference.

If you will be using this tablet all day long as an artist, go for the DECO 02, if you will use it casually or not for artistic purposes the G640 is a great fit.