Ipaint47,
This comes up a lot and really depends upon the application/technique. Typically the longer rods are used for throwing search bait lures (swimbait, spinners, cranks, etc.) for the extra distance (when properly matched with the lure weight). The length is also useful for leverage when pulling fish out of junk (flipping, pitching, etc) or sweeping hook sets - T-rig, C-rig. Longer rods are also used for jigging around submerged trees, brush, vegetation mats, etc., where you want to work the lure all around where the fish are holding but can't or don't want to get near the structure.
The shorter length is good for accuracy. Skipping, throwing around cover, etc. For me, I am just as accurate with a 6'6" to 7' rod and think most are as well. To me you have to get down in the 5'6 to 6' range to get the spot on deadly accuracy - ie hitting a coffee can as compared to a wash tub. Also, keep in mind that part of accuracy is due to the action of the rod. A fast action rod - in most situations - is going to be more accurate than a similar power and length slow to mod action rod - its all about physics.
OK, enough of the boring physics/mechanics stuff….
You mentioned top waters and plastics. These techniques are very different: Top water is more search related, typically heavier lure, slack line and a treble hook application where plastics are more strategic, typically a little lighter, tight line and a single hook application.
I would recommend a Med power and fast action in a 7' length. The reasons are that I don't think the accuracy is that drastic between the two lengths and you need a good "middle of the road" rod for these techniques. You will have more options with a 7' and have the additional length for distance - you can make a long rod cast shorter but you can’t make a short rod cast longer ;^).
Plastics require more power to drive the single hook through the fish's mouth/lip. To set the thicker single hook the rods power will need to be brought into play immediately (for thick/tough lipped fish like bass - not soft like Crappie). Getting into the power of the blank is a function of action so a fast action rod is the choice. Whereas with a treble you just need good contact due to the fact there are three points that are thinner and easier to penetrate - less power needed. But, given the mass of a top water lure it is easier to throw. So, with the fast action rod with top water lures you will have to be more attentive to maintaining consistent pressure on the line during the fight - just don't wrench it or make very fast hook set and fighting motions and you should be fine.
Hope this helps.
Eddie
