I just checked http://www.generation-jeans.com reviews and it has some decent score + there were a lot of reviews. I'm guessing it's a French webpage? Can you contact them and ask some questions about those jeans? If they don't respond don't bother.
But I must admit that's freaking inexpensive So I understand your concern.
In my opinion, in general, DSQUARED2 jeans fit much better than Diesel but they are much more expensive. It also depends on the body shape and cut of the jeans. But I think in general DSQUARED2 jeans fit better.