It depends on your playstyle, I don't think there is a single 'best' setup. If you follow the crowds and party a lot, then +Dex and +Str.
However, some people do not play a BH like most people play other classes....trying to level quickly. A Bounty Hunter's strength is their profit making potential from spoils, right? To maximize your advantages then, it might make sense to try to maximize your 'Spoils per Level' rather than your 'Exp per Hour' (which most players seem to do by default).
To do this, you probably want to solo green mobs that have both valuable spoils and good quest returns. It take a bit of research into the spoil tables, quest tables, and current economic conditions to do this. You will also level up slower, but what is the rush anyhow? The joy of the game is the journey, not the destination. If you do it this way you will find that you will end up delightfully rich, buying extra armor sets so you can look nice in town for example, rather than struggling to get a single armor set to hunt in....like most of the fast levelling DDs.
I have:
+4 STR, -4 CON
+4 DEX, -4 CON
Tallum Heavy set + Elysian SA Health (Haste don't exist in A one handed blunts,exept the new Dino Island Recipes :( )
Actually your Max HP will drop but I guess you have many :P
Also depents how you xp with BH. From 55 to 65 its a good PvE setup (also for solo) if you are equipped with BW Heavy and AOBA-DMG SA Haste, you only need VR to go xp well enough.
For Mass PvP it's also good cause noone hit the dorf :P Allways try to kill Healers/robes/Light armors first so you can run arround and have fun on stunning people :P
Also your stun is landing better cause of +STR. Your spoil is casting faster of + attack speed.
The only thing that sucks is that you will become a stunny bunny in PvE as the PvE stun success is depending from the CON but I guess you can't have them all :P