They are not all that similar in image characteristics. To be honest I would say that once you are into pushing territory the speed differences between XTOL and Microphen are probably trivial. Having said that, they do look different (although again when pushing, all bets are off in terms of image characteristics). What I mean is, XTOL is significantly finer grained than Microphen under normal circumstances, but since I don't push film I can't tell you what happens in that scenario. One thing that can make XTOL good for pushing in general is that it compensates more than more typical Phenidone-based formulas like Microphen. But a semi-traditional film like HP5+ might just look better in Microphen than XTOL. Just some thoughts.