I have found that for my purposes 1 rain suit will not do. I fish all year and want to be dry whether it is hot or cold. I have frog toggs, regular gortex, 100 mph gortex, and insulated heavy gortex.
If I were limited to only one it would be the 100 mph. That is the only suit I have ever worn that keeps me totally dry.
Also, get bibs not pants.