Well, they are different sizes. Personally, I like the 730 better, which is why I bought it. It is a larger knife, but only weighs 0.10 oz more, due to G10 instead of aluminum scales. One thing to think about, given where you're from, is that the aluminum may get quite hot in the sun.
If I should choose the best fruit, pack strap and box attacking knife among BENCHMADE products I would choose Model 710 Axis Lock or Model 705 if smaller knife is desired. Axis Lock is rock solid, recurved blade provides powerful cutting if required, handle shape is very comfortable and G-10 scales are better for me than aluminum ones on Model 720.
If you are really going to buy one of the Axis Lock folders (very good idea itself
) make your choice basing mostly on handling comfort. Try to handle all these knives and choose one which fits your hand the best.
Think also about carry mode, which you prefer. 710 and 730 are designed for tip-up carry but 720 - for tip-down.