If you must use a metal link to attach two straps together, treat the connection just like a winch cable and hang something like a heavy jacket, a blanket, or something over it at the juncture so if it does let go, the ends won't go flying.
There is a difference between "towing" and "retrieving." In a tow situation, the MOST weight you'll have on your strap/rope/chain is the weight of the towed vehicle -- and you can only have that if you're pulling it up a 90-degree incline.
In a "stuck," the stuck vehicle may be wedged in rocks so the wheels don't want to roll, or it may be mired in deep mud that adds a lot of suction. Thus the weight you pull to start it moving may exceed the weight of the vehicle by a factor of several times. Ever wonder why "tow" ropes are only rated 5,000 or 10,000 pounds, but snatch straps start at 20,000 and go up from there?
A snatch strap has elasticity. That's useful, because as you hit the end of the strap running, the stretch stores up some kinetic energy, and the release of that energy helps (supposedly) to extract the stuck vehicle.
You don't need that stretch for towing. In fact, you don't really even want it if you're towing very far. That's why chains and polypropylene rope (which doesn't stretch) are acceptable for towing but should not be used for extraction.
And that's also why you don't want metal hooks on a snatch strap -- because of the magnitude of the energy stored. If the rope doesn't have any stretch (such as a chain), it can't store kinetic energy and thus if a hook breaks or lets loose, it won't fly very far, it'll just drop to the ground.
