Use the length rod you are most comfortable with. The longer length rods >12' are coming out because some spider riggers are wanting to get the bait further away from the boat. From what I've seen 12' is the most common used for slow trolling / sprider rigging and 10-11' for pole-in-hand jigging.

Check out the pre-tied minnow rigs BnM came out with this year - BNM Fishing - There are multiple weights designed for fishing a variety of depths. The deeper you fish and the faster you move the greater the weight you will need to keep your bait vertical.