The xha1 out resolves the 5d, But the 5d uses aliasing to make it look as it has more res than it actually does. The biproduct is moire, aliasing on straight lines, ect...
Each cam is just a tool, the 5d, destroys the xha1 in low light, you cant even compare the two, it's that drastic. I would use both, they both have strengthes the other doesn't. I still have 2 xha1's and I love um, still. The way to go is use a citidisk, or firestore, save a ton of time in post.
If you look at this, you will get an idea how they can cut together, because this is xha1, and dslr intercut.
http://www.youtube.com/watch?v=Q273wmdzOR8
Why not use the xha1, for your master, and audio, then use the 5d to go in for coverage, and multi angles? This way you have the best of both worlds, plus Shallow dof, is the best way to make the audience see what you want them to see without a choice. It's the best tool aside from low light the 5d offers.
I honestly like the look of a dof adapter, I think they produce a very organic, filmic look that the dslr's cant match, well, they can, but it takes a lot of work, and adding grain.
As far as people saying the xha1 is outdated, well.. their stupid, there's no such thing as outdated when it comes to creativity, aghain, it's the right tool for the job. If you have any other questions feel free to ask, I have used both cams exclusivly for amny different shoots.