That is like saying should I be a pharmaceutical rep or go to med school ? These are two different fields even if under one large umbrella.
If you registered the domains to sell them you need to think about why you thought you could resell them for a higher price than reg fee. Of course we all have domains that are not selling that one or two could be ripe for development on a topic we know very well. You cannot have lists of domains that meet this criteria, if you are a domainer than most likely you are not a domainer. Some do it, but most do not have the desire,patience, or know how to properly develop the domain into a money making website.
If you are a developer you should probably only be regging a couple domains at a time because you know that a proper website takes time to build.
If you are thinking about dropping names they probably are not good names. Why would you want to develop on a bad domain ? Take your time and think about who you are and where you want to go with domain names. There is no need to rush, have a plan and figure out what kind of budget do you have for fresh regs, renewals and if you are going to develop for hosting and marketing.