I think there's stuff out there to convert jQuery code to Moo Tools code and vice versa. After all, both are JavaScript under the hood.

Wow I wouldn't have realized how much faster jQuery is growing had you not linked to Trends. jQuery does seem easier, especially since it's syntax is very css like. I think that's it's biggest selling point. The article I linked to made me think Moo Tools would be the better choice after you know both libraries, but for now I'm more familiar with jQuery.

I wouldn't worry about using either. The tangled code is likely more the developer who wrote the code than it was either library.