Hi Austin,
As someone who saw quite a bit of use with a Sony TRV950, and then bought a Sony HDV HC7 just over a year ago... I'd say the standard def video from the HV30 (i.e. recorded in HDV and downsampled in camera, or in editing) is probably IMHO generally pretty comparable to the TRV900. Probably a bit better. The HV30 is obviously rather newer technology and got one slightly larger CMOS image sensor chip compared with the 900's older and slightly smaller three CCD chips.
But if and when you watch back the HDV footage in high def, the improvement will blow you away!
As you may already have seen / read, CMOS chips as used in HV30 etc, do have a slight weakness compared with the CCD of the older cams, with a bit of "shearing" distortion with fast pans, and occasionally a bit of "jelly wobble" with the wrong sort of camera shake (shouldn't be too much of a problem on trains though, I wouldn't have thought). But for most users most of the time, that doesn't seem to be any issue anyway.
Just out of interest, had you considered the Sony HC9? Actually, not a huge amount to choose between that and the Canon HV30.
Hope that helps,
Giles.