Dean, I would get neither. The XH A1 only shoots HDV, which is QUICKLY becoming less favorable. I would recommend getting a Sony EX1R if you're a beginning filmmaker. It shoots XDCAM which isn't disappearing for a while, shoots at a significantly higher bit rate and gets a truer white balance in MY opinion.
Video shot on a Canon XH A1 Video Camera tends to have this greenish brown tinge to it even when you supposedly have correct white balance. There is a technical reason for this, but I won't go into that detail. Also, with the Sony EX3, you have more handling options thanks to its ergonomic hand-grip.
But yeah, if the ONLY options were XH A1 or 7D, I'd choose the XH A1 for the same reason Nigel said.