you can do alot with a 10,000 pound strap i pulled cars and trucks with it and never had a problem with mine. basic care for the strap goes along way! look at it like this(not tryin to sway what you want) lets say your truck is like mine a 3.slow you WONT produce enough power to break a 10k strap. now if your going to be doing truck pulls like axle to axle pulls for fun yea id go with the 20k one. price wise i paid about 45bucks for my strap and not so sure but you are going to be dropin about 80+ for a 20k one. in the end anything over 10k will work just fine and the next thing is your driving skills if your good and know your truck very well you will be find. so to answer your question if your pulling the same amount of weight with both a 10k and a 20k strap the same amount of stress is going to be the same nothing changes if your pulling out a 5k truck lets says your going to need atleast another 1k to break him loose so only 6k will only be needed and only 6k will be on stress on both the 10k and 20k straps

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Never tell people how to do things. Tell them what to do and they will surprise you with their ingenuity."
General Geroge S Patton
2007 3.0
automatic trans, 4.10s with L/S
ported and polished TB
4brand new speakers with inslation in doors
smoked tail lights
20%tint on driver and passenger windows
5% tint on back window