There are three types of straps and ill list them in the order that should be the most useful,
First is a kinetic rope, these stretch up to 30% so you can get a good start and it'll store the energy as the rope gets taught, it will also relieve the stress put on the components that a tow strap has when it gets taught. The downside to these ropes is that they can be fairly expensive, a 30ft will generally run any where from 125-150$.
Second is the snatch straps or kinetic recovery straps, these look just like a tow rope. They stretch around 10-15% and a really high quality(arb) strap will stretch around 20%. While not as useful as kinetic ropes because they can't store as much energy they are much more useful then a tow rope because they will also relieve stress on the components. They are actually fairly cheap, any where from 40-90$ is a good price.
Lastly is the tow rope/strap, they don't stretch...At all. So when wheeling these will get the job done most of the time for slightly stuck vehicles, but any thing buried up to axels will need something better then a tow rope. 'yanking' with the tow ropes will cause immense amounts of stress on your towing locations and can be very dangerous. Tow ropes are really garbage for wheeling when it comes down to it but if your helping a friend who is barely stuck this might be a ok option because a good tow strap will only run from 15-30$ depending on the size and the strength of the rope.
Some good companys for kinetic recovery ropes are:
Bubba rope
Masterpull
ASR
Viking
A good recovery strap is the Arb, I don't know of many others because I haven't researched them enough.
Tow straps are very generic, the general assumption for tow straps is that every inch wide a tow strap is, the breaking strength is # of inches X 10,000lb so a 2 inch strap is more or less 20,000 lb. A 4 inch strap would then be 40,000 lbs and so on. If you have a harbor freight near you that is where id go, normally they have a 2in X 30ft for around 20$, online you can find tow straps for about 15$ but then you'll have to pay shipping and wait.
Well I hope this helps!