The first is an emboss, which is obvious because its stamped into the paper. I would hold it up to the light and see if there is a watermark.
The second is a watermark, only visible when held up to the light, and if I remember right, this also has an emboss which is the wording in which is darker that says Aquarel/Arches in all caps. This is much harder to fake, and is used in currency to show its legitimate ( you can often see it in paper money, like the US dollar ).
Unless they are defective, i would assume both are the real thing. But the first is pretty easy to fake, can make a die that does that and get letterhead made, for less than a hundred dollars. The second requires the mill making the paper is doing it, which really isn’t something someone would fake.
I would say they are both ok. I think the second is an older way of doing it, i dimly recall this but lately the watermark is a bit obnoxious.