The rapid-torch flamer's stats are almost identical to the stats of a regular flamer. The only element different compared to the normal flamer is attack animation. The difference in animation does have actual in-game impact, although minor. With the rapid-torch flamer, it's enough to quickly tap with mouse or trigger to fire the flamer, expending 1 point of ammunition in the process.
With the regular flamer, there is a slight delay before the gas get ignited which then propels fire, so in order to just expend 1 point of ammunition one needs to hold fire button a little bit (but not too long to expend two ammunition points). Therefore, with the rapid-torch, one can conserve ammunition a bit better than with a regular flamer.