What is equivalent to MATLAB griddedInterpolant function in python?
Those two functions are equivalent. However, MATLAB's griddedInterpolant has multiple interpolation methods, whilst RegularGridInterpolator only seems to support linear and nearest. With MATLAB, this gives you more possibilities to choose a proper method given your data.
Your two results seem to be accurate to the 12th digit, which in most cases is a good accuracy. The difference between the results is probably due to different implementations of the interpolation method.
If you want accuracy beyond the 12th digit you should rescale your problem so that you only consider the decimals.
I tried scipy.interpolate.RegularGridInterpolator but MATLAB and python give me results with tiny different (For example: python: -151736.1266937256 MATLAB: -151736.1266989708). And I do care about those different decimals.