After pryd I find it rather difficult to tell est from dest.
In some sentences the context provides a clue, but in this case either of the two make sense, so in conversation the difference can only be heard.
Has this difficulty been experienced by other learners?
My wife and I have both tripped over that kind of thing (can't recall for certain whether either of us has hit that exact example). In several languages (we both speak fluent French, some German, and a little bit of Dutch, Welsh, plus a few words of Spanish, Greek and Japanese). Due to mild hearing loss I've even tripped up that way in English once or twice.
You can practise discriminating between the two if you go to, for example, http://www.textaloud.com and type in something like "pryd dest ti, pryd est ti, pryd dest ti, pryd est ti, pryd dest ti,...." a dozen or twenty times and them listen to the result.
It is hard to do to begin with, but the computer voice does pronounce this one quite well (not always the case, as we explain in several places) and the difference is definitely there.
In practice, of course, there is usually sort of conversational context which helps to avoid any confusion.
Using ear/head-phones may help. You can probably find a way of tweaking the sound output, too, to boost frequencies where you might have a problem with less than perfect hearing. If you have software such as Audacity (open source and free) you can also slow down a sound recording without changing its pitch.
I do hear the difference, when pryd dest ti and pryd est ti are spoken one after the other.
The pronunciation of pryd dest ti reminds me closely of the type of sound I recently enquired about (The pronunciation of double consonants).
The 'D' in pryD Dest ti sounds to me as a double consonant (not a Welsh 'DD', of course), that is slightly stronger than in pryD est ti, as EllisVaughan wrote about the NW pronunciation of double N's and double R's.
As it happens there is a word pryddest!
It is the generic name for a type of long, free-metre poem. The Crown, one of the major prizes at the annual National Eisteddfod of Wales, is awarded to the poet who submitted the pryddest that has been judged the best of those meeting the necessary standard that year.
(The Chair is awarded for the best strict-metre poem.)