Rik...depends on the line mate. Have a look at the Fuji site for some very interesting info on reel spool sizes and ring spacing.
Basically, Fuji reckon that up to 120 yards or so, with 12 pound nylon, there is no decernable difference in casting distance between a standard and "sea casting" spool. This has been voiced by several well known BIG casters recently..Frank Warick for example. Heavier lines are a different story however, and so are braids...so I would go for a bigger spool if needing to go further than this distance.
As for ringing...Fuji, who know a thing or two about rings, reckon that having few and large rings CUTS DOWN on distance. I agree. Get a rod with long range ringing and thread some line through. Pull the tip into a curve and feel the abrasion. Then note how the line moves out the tip ring as the curve increases. Basically u are losing all that energy as the line does not follow the rod curve like it should.
Fuji now say that that is why a multiplier rung rod will outcast a fixed spool rung rod...because it has more rings so the line loses less energy under a compression stroke of the rod.
Its interesting reading.
I would base my choice on the distance I was fishing, the line I was using and the style of fishing I was doing. Basically, sub 120 yards, standard Baitrunners, aboive 120 yards with 15 pound+ line or braid, the new big casting shimanos. Hope this does not confuse anyone