Wow... lots of 'hate' on the neons (not really, but not a single vote for the neons)!
I vote neons! I have kept neons since I was a kid. I have kept neons myself for a long time, and still have a shoal of 9 neons. The neons are from a local mega-chain fish store. I only buy them when they are $1 each, and I've NEVER, not even once, lost half of them at once. In fact, they have been some of my hardiest fish to have kept.
For example, I had a problem tank at work, and it killed bloodfin tetras (commonly described as very hard), but the bloodfins died in the tank within hours (12-24). I tried to figure out the problem, fix it, tried again, same result. The neons went into the tank and they are still swimming. My original shoal of 20 neons from 4 years ago is now down to 9.
I will concede to TLM that the cardinals have more red. They are also larger, so you can't have as many as you could neons. And for me, the added neons adds a little something to the appearance.
Anyway, I don't want to dissuade you from the cardinals, but I wanted to add a good word for the neons. I've done some very informal observations and it seems that UKers are having much more trouble with neons than USers. Perhaps there's an issue in the breeding stock over there, that's not an issue here. Not sure, but that's just something I have noticed over the last few years.