Differences between ProRes and DNxHD:
(Not all, but first that comes to mind)
Prores is VBR, DNxHD CBR
Prores is ALWAYS (at least) 10 bits, DNxHD only on the 'x' flavours
Prores is resolution independent, DNxHD has a flavour per resolution, and that is a limited set
Now, there is a (cheap or free) solution to get ProRes out of your PC PP, based on a trick that it hooks into the frameserver PP seems to have.
But, DNxHD is no punishment, so if you have a decent flavour, just use it.