Hi again Chris (we've got to stop meeting like this )
I can't tell you 'the best' because I've only used 1 kind (doing vermiculite bottoms in Ct and Va, both companies used the same one). The name is Whittimore and with a very few exceptions, has proven to be an excellent product. I have used the 'pre mixed' vermiculite and found it to be lacking in both trowel-ability and ease to mix. The key to getting good results is keeping all the mixes as close to the same ratios as is humanly possible (until a new 'mix guy' gets his 'eye for how the mixes should be, I mark 2 'fill lines' on a 5 gal bucket (the first for "fill to here 2 X' and the second for "then add THIS much") ) Hope this helps, any other ?s - just ask - Waste