In the EXO3 16x19 you might find more control and lower power with a stiffer 16g gut main such as some Pacific products or BT7-based VS Touch.
As for durability, 16 might be marginally more durable but in a gut/poly hybrid the difference won't be so decisive that you should base your choice on durability over playability. I'd focus more on the feel than durability.
What gauge Outlast are you using? I've been curious about that as a cross for gut mains.
Only on Talk Tennis can you find people who believe
that 10 feet of lead tape has no effect on a frame...