I'm nearly as big of a fan of the little 20 as Roy , but honestly , if i had the choice to buy a low klm rb25 in good condition , id put the 25 in , sell the 20 to make back as much as i can and enjoy the slight increase in torque . Note : the best part about the lil 20 is the way it revs all day if in good condition , 25 won't take stupid limiters set at 8500rpm for very long from my experience . If the 25 was just another wrecker motor that you didn't know the condition of , i would suggest the 20 all day