Depends on what you want from them.
As everyone will say, hk47 would be best as a driod squad leader.
47 is a big dollop of sturdy self res goodness. Comes into his own when throwing grenades into groups of Jedi.
88 is made out of papermache but armed with a howitzer, he can deal an immense amount of damage.
If your sticking to a droid team,its 50/50 choice if you already have poggle maxed.
Did you make a choice?