Numerically and statistically, any gap between two people who are Planet level is going to be astronomically greater than that between two people who are Large Building/City Block level. In terms of battle power, that'd also be greater when considering the difference in Ki between most fights in Part 1 wouldn't even be 2x when considering what scouter numbers imply.
In terms of the more standard differences in capabilities though, probably Tenshinhan and Yamcha. Yamcha beat Reacoom easily, but not to the extent of deflecting an Eraser Gun with a kiai or oneshotting him with a kick like Tenshinhan did to Yamcha and his Kamehameha.