That there is a loaded question, to be honest the best plastic is the one you find works best with your methods I will give some of the feedback I've read and have experienced.
Lurecraft is a good plastic in the finished product I had 5 gallons of medium and I liked it a lot the one drawback was it hard packed quite quickly, hardpacking is when the solids fall out of suspension and becoming a hard layer on the bottom of the bucket it can and does reincorporate but its a pain, with all respect I would call Kim and ask if that has been resolved as this was a few years ago and maybe the formula has changed.
Calhoun has a smoke problem when heated its a fine line between bringing the plastic up to the right temp and smoking it also has an oily finish which some liked some don't.
Chemionics I currently have 5 gallons of supersoft its good overall but I'm having a micro bubble issue, could that be atmospheric its possible and its not the end of the world the finished product is nice.
Do-It has been having a yellowing problem and the price point is a little high for me but again contact Jerry to see if it's been reformulated and or corrected I know their aware of the problem.
Ispikeit/lureworks by far has the most options the price point is good they are very friendly when contacted about product and did I mention the price point is good. The thing is I can't give you my personal experience as I've yet to try it, it's next on the list.