UTG: 90.58 BB (VPIP: 31.06, PFR: 12.42, 3Bet Preflop: 1.69, Hands: 164)

MP: 105.74 BB (VPIP: 16.90, PFR: 15.49, 3Bet Preflop: 8.33, Hands: 71)

CO: 290.94 BB (VPIP: 31.65, PFR: 16.46, 3Bet Preflop: 7.14, Hands: 80)

BTN: 120.92 BB (VPIP: 68.12, PFR: 40.58, 3Bet Preflop: 12.00, Hands: 71)

SB: 100.5 BB (VPIP: 21.36, PFR: 14.16, 3Bet Preflop: 2.33, Hands: 229)

Hero (BB): 164.34 BB

SB posts SB 0.5 BB, Hero posts BB 1 BB

Pre Flop: (pot: 1.5 BB) Hero has Kc Qs Jh Kh

UTG calls 1 BB, fold, CO calls 1 BB, BTN raises to 5.5 BB, fold, Hero ??

BTN has been playing very aggro, with 68/40/12 and isolating limpers a lot as well.

Should I 3bet this decent KKxx, or just flat and hope to flop big?  We haven't had 4bet pots, and he has been fairly straightforward postflop, c/f'ing a lot when he was OOP.