People love Nichia’s because of the tint and color reproduction (CRI). Depending on your eyes, the difference between a Nicha and a low-CRI cree could be very dramatic, or not so much. Personally I really like the light a Nichia produces, but I only have one of them because efficiency is more important to me.
The 219b is newer, and a significant increase in output over the 219a.
This thread could be helpful for you.
I have mine in a P60 at 2amps, but the Nicha on copper can be pushed past 3amps.
The price is a little higher than an XPG2, but it’s not ridiculous. You owe it to yourself to try a Nichia at least once.