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The 430EX II is actually quite a capable flash and I use mine frequently for similar situations.
One thing that generally isn't appreciated about Canon flash is that the metering is done entirely in the camera. So unless there is something physically wrong with the gear, either flash should produce identical exposures on the same camera body under the same conditions. Of course, do a test if you are not sure.
In similar situations, I always try to balance the flash with the ambient light so that the background is not a black inkwell, usually something like a 1:4 ratio, so my settings are usually similar to Gunzorro's. Shoot on M mode unless you have a good reason to do otherwise. I would add the following thoughts:
1. If you will be dragging the shutter at all be sure to enable 2nd-curtain sync on the camera (I just do this religiously for all indoor flash). If there is streaking in the background it will look natural this way and minimize ghosting.
2. I recommend not trying to color balance the flash fully with incandescent lighting, as I've never liked the look of a full CTO correction on the flash. Instead, I use a 1/4 CTO gel at most and set a Kelvin WB of around 4500-4800 which gives a nice effect--the subject is lit correctly by the flash but the background lighting remains warm and inviting. (This is all a matter of taste, so try it yourself to see what you prefer.)
3. Black tuxes and white bridal gowns can wreak havoc with automatic flash metering, so check your histograms. Remember that direct flash can use distance information from the lens to help with exposure; if you pull the flash off-camera or tilt the head for use with a light modifier, this is no longer possible, so even more exposure variability can be expected. Shooting RAW or RAW + JPEG is a good idea.