Drought
Dry Skin, while it would allow it to wall Politoed, Tentacruel, Jellicent, etc. and gain great passive recovery, it would neuter its Fire offensive typing, thus making it an inferior Toxicroak offensively. It also prevents it from working well in sun, thanks to it losing one-eigth of its health because of said ability, combined with the fact that it's "weak" to Fire in said condition. These factors combined mean it would be an inferior ability to Drought.