IELTS Life Skills and IELTS may both be used for family settlement entry clearance purposes.
The immigration rules require a minimum A1 level for speaking and listening foe entry clearance.
IELTS Life Skills at B1 level will be accepted for ILR and British Citizenship

IELTS can be used where IELTS Life Skills are used, but be aware that IELTS candidates must reach a score of 4 in both speaking and listening.
This is equivalent to the higher level B1
The scores for reading and writing will be ignored regardless