yeah if you think about short esters, depending your fat level, metabolism and other factors, things like prop can be gone within a few days. that means the majority of what you inject in a given week is actually hitting your system that week.
so 8 weeks on 500mg a week of prop is 8 weeks at 500 (basically.... and not accounting for ester weight for the sake of using a nice easy number like 500)
but 8 weeks on 500mg a week of enan would be like 100-150mg the first week, in the 200-low 300's the next week and then would go OVER 500mg a week for several weeks and then fade out the same way when you started it. so you'd actually be getting 500mg a week x 8 weeks over the course of like 10-12 weeks total time. slow build-up, slow fade-off, and then a peak of several weeks getting more than 500mg of hormone releasing into your system in any given week.
so you can see how that varies from the prop a bit. hit higher peak levels, building up slower and steady, same for the drop-off. the differences i suppose could have an effect on sides (as in more sides from your blood levels rising and falling more with prop.... more sides from the enanthate hitting higher peak levels.... etc.) but in the end it should be pretty similar.
of course, i might have it screwed up. that's just how i understand the ester cleavage.
and really, the prop is probably a bit slower on average, so the difference should not be huge between the two as far as peak levels reached and what not.