They're both fishing metaphors and they both make just about as much sense.

https://grammarist.com/usage/trawl-troll/

well, today I learned troll has other verb definitions.

I think "trawling" is a lot more common, "trolling for cock" is the exception where it's always "trolling" and never "trawling".

Probably regional dialect. I spent my teenage years "trolling" for just about every part of the female anatomy, but never heard anyone use the word "trawling" in the same way. That said, trolling is a much more popular fishing method where I'm from.

In fishing isn't it a question of volume? IIUC trolling is moving very slowly/wakeless with a small number of lines, and trawling is a big net that catches everything?