I bought the Canon HF 10 which captures at 1920 x 1080 and I can get the Canon XH-A1 at a bargain price. Looking at the spec of the A1 it says it captures at 1440 x 1080. Does that mean that the humble HF10 captures at a higher resolution than the A1?
While AVCHD is a more compressed video codec- it doesn't necessarily mean it has lower image quality. In fact, in terms of outright resolution- the A1 (of which I've owned) shoots to HDV and thus can only record 1440 res whereas the Vixia will record 1920 as allowed within AVCHD consortium specs.
Since the HV20/30 have VERY similar image characteristics to that of the A1, and it's been compared to the Vixia's 17mbps bitrate footage of which the Vixia was deemed "better"......I wouldn't agree the XH-A1 is superior- just more adjustable.