I will say this about the current Democratic field: all of them are better than Trump, and most of them are likely to be really good (and progressive) leaders. Yes, Gillibrand and Klobuchar are more centrist, but other than to the chunkstyle voters, would be considered progressive in most circles. Gabbard I am reserving judgment on - because of her anti-gay associations. Biden has skeletons, let us not forget (although I do love Joe).
My hope is that the field remains positive in their competition (and there are others yet to join). I happen to think Cory Booker has the strongest credentials (as a lawyer and having been both a Mayor and Senator).