Barge cement gets my vote. I buy it by the gallon and keep a gallon of thinner also. It's pretty important to keep it at the proper thickness and also learn what tacky level to press it together.
The shoe shops use two coats for the best bond.
Here in the saddleshop I use one coat on some parts , two on parts I never want to move.
The new formula is not as good as the old but is still better than all others for leather. Where it really shines is for wet leather. It's the king for wet formed sheaths, or saddles for that matter.
When you press it together, a light tapping with a snob hammer sets it.
RS