Contemplating getting a 6" senko mold, but I've got a choice between a .45" diameter bait (pretty standard size, roughly the same as the Yamamoto ones) measured at the egg sack and a .65" diameter.

Works out that the bigger one will likely take more than double the plastic material than the thinner bait for the same length, but while that will definitely displace more water I suspect the extra heft will reduce the fluttering action - so I'm not sure which will have better drawing power. I'm intrigued by the idea of a heftier bait - up north a 6" senko is uncommon - a larger profile still will be even more unique.

Wasn't sure if anyone else has tried a more heavy bodied senko compared to one of similar length and compared the actions.

Thinking more on the extra mass of the similar sized bait, it might make it easier to skip as it will have more momentum.

Flip side, it won't work with my O-Ring tool...

Just go to Lowe's and buy a pac of larger O rings, which is what I did for the Senkos and I lube the worms with Smelly Jelly to slide them on slick as a whistle.  As to if bigger is better I would guess it is a nice option to have on hand.