These two circuits are an ultra high swing current sources (on the first schematic is lack of biasing branch for VBN and VCN so it hard to call it as mirror).
The first one was presented first time (as my best knowledge is) at 2002 in the IET Electronics Letters (don't remember details), while second was published in Elsevier Microelectronics Journal ca 2011.
The first one using only negative feedback (there is double boosting applied) to achieve the most flat output characteristic with output resistance in range of K_1×K_2×K_4×r_3 (where K is an intrinsic gain of each mosfet) and can have very low Vout_min (my experience is as low as 25mV, however it is set by biasing circuit). Due to high gain feedback it would required compensation at gate of M1.
The second circuit has using both negative and positive feedback loop (M3→M1→M2→M4 which are moving minimum Vout to lower values), and now I have seen this circuit is not a mentioned by me UHS CM from MJ_2011 ;-). It doesn't has a 3 MOSFETs for negative feedback boosting an output resistance. If you could share with more info where did you found the second scheme, it would be useful to discuss.