What the difference/advantage/disadvantage ?

[PATTON, BILLY \(SBCSI\)]

short versions of lists
I have  This 

projs:= a b c
bb+a := d e f
bb+b := g h i
bb+c := j k l
tp+a+d := m
tp+a+e := n
tp+a+f := o
tp+b+g := p
tp+b+h := q
tp+b+i := r
tp+c+j := s
tp+c+k := t
tp+c+l := u


probably not syntactically correct.

define proj
$(1) : $(addprefix bb,$(addprefix +,$(projs)))
endef
$(1)+$(2)$(eval $(call proj,$(proj))))

define proj_bb
$(1)+$(2) : $(foreach topic,$(tp+$(1)+$(2)),$(1)+$(2)+$(topic))
endef
$(foreach proj,$(projs),\
  $(foreach bb,$(bb+$(proj)+$(bb)),\
    $(eval $(call proj_bb,$(proj),$(bb)))))

define proj_bb_topic
$(1)+$(2)+$(3) :
  echo $@

################
#  VS
################

$(projs) : $(addprefix bb,$(addprefix +,$(projs)))

$(addprefix bb,$(addprefix +,$(projs))) : $(foreach proj,$(projs),\
                                            $(foreach bb,$(bb+$(proj)),\
                                              $(tp+$(proj)+$(bb))))

$(foreach proj,$(projs),$(foreach bb,$(bb+$(proj)),$(tp+$(proj)+$(bb))))
:
  echo $@