Inusagi, when you say it's "soo hard...", what exactly are you referring to? Are you saying it's hard to solve? Hard to turn? Or hard in another way?
If the puzzle is hard to turn, you can and should return it to Puzzle Proz for a replacement. I bought one from him (the same that you have) and it turns just fine. No, it's not a super-speed megaminx like I imagine the Mefferts must be, but mine turns easily and yours should too. If yours doesn't it is defective and you are entitled to a replacement.
If the puzzle is hard to solve, well that's what makes it fun. And the challenge would be the same regardless of which Megaminx you own. So yes, you bought the right one.
There is another type of megaminx, besides the Chinese one and Meffert's. I just happened to order one recently, and I just received it yesterday. You can see the listing for it
here. In case you're interested, I'll share my first impressions.
This puzzle feels
much more solid and stable than a Chinese Megaminx. Consequently, it was very tight when I first took it out of the package. I lubed it with silicone oil, and now it turns very smoothly. I am able to turn each face with a single finger. I can't exactly cut corners but I can turn the right face even if the up face is mis-aligned, which brings both faces into alignment. Perhaps the cutting corners thing is my lack of skill rather than something lacking in the puzzle.
The faces on this puzzle are a little thinner than on the Chinese Megaminx, which makes the edge pieces a little wider where two colors join. For me, this makes those teeny-tiny little edge pieces a little more prominent and easier to find. Also, the centers are bigger than on the Chinese Megaminx. I think this might be why the puzzle feels more stable, but it will take a bit of getting used to. Also, this puzzle doesn't click at each turn like the Chinese Megaminx does; it turns more like a regular Rubik's cube.
On the downside, the stickers that come with this puzzle are (in my humble opinion) complete crap. There are three different dark blues, which closely resemble each other, and two different light greens, which also closely resemble each other. You have to sticker the puzzle yourself, and I had a heck of a time figuring out which color to put on which face so that the like colors weren't adjacent to each other, and so that I wouldn't confuse one with the other (hope that makes sense). I found stickering this puzzle to be a royal pain in the you know what, and immediately went online and ordered replacement stickers from Cubesmith. Now I hope they'll fit. If they don't I'll have to figure something out - I'll either cut my own stickers or paint each face with a different color nail polish.
Once I get new stickers I think I'll be very happy with this puzzle. Since I just got it yesterday, I can't tell you how well it will hold up over time. Hope this helps, and good luck with your new megaminx.