Miller Urey experiment ignored many conditions in the atmosphere that would breakdown the chemical synthesis they did achieve e.g. cytosine - has no chemical pathway during earth's primordial past, the gases Miller relies upon - consume the chemicals that create this necessary component of nucleic acids. Ribose, phosphate compounds also create problems in Miller's scenario.

deep sea hyrdothermal vents would actually inhibit life formation. Experiments show that amino acids could form in these vents but only have a a half life of a few minutes - some sugars last only a few seconds. No RNA/DNA, peptide formation - and, worse, ammonia can not exist in levels necessary for life in these vents. What characteristics of these vents that would allow life - also destroys life. Schoonen, Xu - Astrobiology 1, (2001) pg 122-123.