If I lived in an are where such things were needed, I think my main considerations would be,
1. Grips wear out and need replacing less often than gloves.
2. The grips are always there and won't ever be forgotten or left at home because it seemed like such a nice day.
3. You don't have to remember to plug in the grips when you start riding and you don't look stupid when you stop in front of a lot of people who know you and try to walk away from the bike while your gloves are still plugged in.
