In my opinion, D.peltata is the easiest tuberous sundews to grow. I successfully grow mine all wet all the year without any problem, and it is very tolerant to environment variation. Since I don't have a lot of others tuberous species, i can't say a 'total' yes to this, but for me, it is.
Note that an author, J-J.Labat, said that he consider D.menziesii as one of the easiest to grow. My seeds sprouted few weeks ago, so I'll be able to confirm this during this year.