I say whichever you can afford or what is available if you want to buy now.
if you need high quality audio then you need the 205, if you just want stunning 4k picture quality with ok sound then the 203 will work just fine.
As of right now there are still a few new 203 left for sale
I think all the sane priced 205 are gone, avoid the $3500 ones on eBay like the plague!
It looks like Oppo may do one final extra run on the 205, go to their sight and you can register by email for them to contact you about availability if they go ahead.