this is a bit of a hot issue.

FAN LEAVES:

POSITIVE many growers remove about 1/2-2/3 of them in the idea that more light will reach the bottom branches, causeing bigger buds

NEGATIVE fan leaves are the plants largest surface area for collecting light, and you deprive them of that ability by removing them


LOWER BRANCHES

POSITIVE removing the bottom branches will focus all growth into the fewer, but now larger, top colas

NEGATIVE the plant is being shocked, and its recovery efforts may use up that acclaimed extra energy