Helper Light Groups vs Zigbee Groups?

Hi There, I switched over to Zigbee Groups but have seen some weird things. like I have 3 downstairs ceiling lights. I have two Zigbee groups, 1 for all of the lights and another 1 for just two of the lights. But both of them turn on all the 3 lights. Any one have any susggestions here or is it better just to go with light groups via a helper?