The X41 had only a swiveling screen, pen and a couple of physical buttons on top. It did not come apart into two parts.
The two laptops serve different users. You could say that the X41 is primarily a laptop and a tablet secondarily, while the Helix is primarily a tablet and a laptop secondarily.
The tablet is easier to carry, and might therefore be preferable if you are going away/travelling and you don't think that you will be typing much. The X41 is when you do mostly traditional computing and you need tablet functionality only sparingly.
The X41 had a dock also, for desktop use. I would like to see a (vertical) desktop dock for the Helix tablet so that I can use it with a desktop screen and keyboard, and without having to connect the keyboard part first.