Hi. I have driven Tamiya's and they are good, but the parts tend to break a bit more easily than the Xray's.
The downside is that the Xray parts do cost more, so it depends on whether you want to replace more cheaper parts, or fewer expensive parts.

If you're mainly running indoors on carpet, I would recommend the Xray out of the two as it's easier to drive and setup. I'm sure the new 418 will be good but there aren't too many drivers here in the UK with Tamiya's so setups are harder to find.

Skiddins