We have performed a comparative analysis of three recent and reliable SnIa datasets available in the literature : the Full Gold ( FG ) dataset ( 157 data points 0 < z < 1.75 ) , a Truncated Gold ( TG ) dataset ( 140 data points 0 < z < 1 ) and the most recent Supernova Legacy Survey ( SNLS ) dataset ( 115 data points 0 < z < 1 ) .
We have analyzed and compared the likelihood of cosmological constant and dynamical dark energy parametrizations allowing for crossing of the phantom divide line ( PDL ) .
We find that even though the constraints obtained using the three datasets are consistent with each other at the 95 % confidence level , the latest ( SNLS ) dataset shows distinct trends which are not shared by the Gold datasets .
We find that the best fit dynamical w ( z ) obtained from the SNLS dataset does not cross the PDL w = -1 and remains above and close to the w = -1 line for the whole redshift range 0 < z < 1 showing no evidence for phantom behavior .
The LCDM parameter values ( w _ { 0 } = -1 , w _ { 1 } = 0 ) almost coincide with the best fit parameters of the dynamical w ( z ) parametrizations .
In contrast , the best fit dynamical w ( z ) obtained from the Gold datasets ( FG and TG ) clearly crosses the PDL and departs significantly from the PDL w = -1 line while the LCDM parameter values are about 2 \sigma away from the best fit w ( z ) .
In addition , the ( \Omega _ { 0 m } , \Omega _ { \Lambda } ) parameters in a LCDM parametrization without a flat prior , fit by the SNLS dataset , favor the minimal flat LCDM concordance model .
The corresponding fit with the Gold datasets mildly favors a closed universe and the flat LCDM parameter values are 1 \sigma - 2 \sigma away from the best fit ( \Omega _ { 0 m } , \Omega _ { \Lambda } ) .