I don't develop, it doesn't appeal to me, i prefer to park them, it's hard to tell which parking service is better, because it all depends, i think most domainers change and test all the time.
What i really like is to sell domains, i don't really think that developing a website adds value to a domain, a good name should sell itself to the right buyer, i always think i sell domains not websites.
That's my 2 cents on the subject, but you should do what you like, i believe that's the first essencial key to success, enjoying what you do