The main trimming
winches are usually set up in pairs, one called the "Primaries" one called the "Secondaries"
The "Primaries" are usually the larger set, near the cockpit. They have the most leaverage, or lower gearing, allowing you to handle greater loads with ease.
The "Secondaries" are usually smaller, with less leverage, higher gearing, and faster spinning. They can be placed just about anywhere, as ling as you can get a fair lead to your blocks.
On the J-105, the "Secondaries" are on the cabintop, the "Primaries" are on the cockpit coming.
As you noticed, you have a better view of the headsail, trimming from the leward "Primary" when going to weather. You will also be able to make finer adjustments and be in a better position to "Work the slot" from there.
When you pop the "chute, you will probably find that you are better off cross sheeting to the weather Primary, a better view of the sail from the "High Side".
In every situation, and for every crew, there is always some compromise that might need to be made. You should work with the rest of the crew to find out what works best for the team and the boat as a whole. You may find that a little sacrifice in your comfort trimming the
jib might make the boat a little faster.
Good luck and "Go Fast!"