The reason why you prefer Eflat instead of D# is because it is another layer of expression and while my explanation does not give full justice because it involves such an endless set of factors but to use an analogy as a test on yourself may be an easier way to explain this: if you try to imagine that the shadow of D# is Eflat. and see how this affects your expression in playing. While saying this, the full truth is that D#and Eflat, and even the name "D" and "E" nor "#" nor "flat" have anything to do with your question at all and it is actually the sound and expression which you are talking about itself and this is where micro vibrations and pitches come in through the human body,instrument or voice, but are not consciously picked up as easily. Music is like a live concept and source and to express music in your own personal way and language where you feel more comfortable with is also found for all the famous composers who also preferred different keys over others, and so you are not on your own It involves every aspect of what you are and your expression. Concepts are formed by sound and music , for example you can test your thoughts for this, for example. If you walked on stilts because you like the feeling of it being pointy what kind of music would you play and what key/s or tonalities would you play music to express this in? or if you think of a concept such as you are existing underneath the curves of a shape and that inside this curve there is a musky velvet shadow and a fragrance to it, so then what key/s or tonalities would you express this in music? you will find it already exists before you even got there to experience it. And more importantly would be; what will be the difference between your expression if you were to play both of these examples in the key of D# and both of these examples in the key of Eflat? Without applying such concepts to art it will be challenging to give the words justice in explaining it. Concepts are what drives music towards us. It is our own imagination, senses and exploration which discovers these music concepts through our own interpretation and expression as there is a difference between the force and energy of music and your own expression of music yet the music will adapt to you because it encompasses pretty much nearly everything. In the same manner our reality is only a shadow of a much greater reality as if we are walking in the shadow of a gigantic tree but we don't see the tree and we only see the shadow it creates, and is only because our minds only know in part. Einstein put it very well with his quotes: Logic will get you from A to B. Imagination will take you everywhere. and he also said: The true sign of intelligence is not knowledge but imagination. In other words everyone can do this if they let it happen and yes it can take time unless you are a young child. Many years ago now I was doing my own research project (1981)and discovered and/or invented a new genre of music. I don't know whether to say discovered or invented for the reason that I know I invented the way to get there and the methods but for what I found is impossible to be created by human hands or computers and already exists but it goes against all natural laws yet it does not destroy but it could if it went against its own laws by some reason, and so I either discovered or invented new instruments and sounds and music . I still have not published it and not because I don't want to but because of the implications it will have and so the answer to your question is this, do what you feel comfortable in doing because you will be relaxed both in your mind, body and soul and as long as you have good thoughts inside you and you are not afraid of anything, not even your own darker thoughts which are negative and overcome them with what is pure you will find the wisdom and truth and believe that you can go through it. If you do this you will go on the right path because the truth is undeniable and you will no longer worry about why you like D# less than Eflat because both of them have their own purposes and within this, is a world within each one and laws within each one which no one can alter or conquer and that is the power of music and sound. It is a gift so wonderful and we need to appreciate it and you also can appreciate your weaker parts within you so that no matter what key you think about you will express freely.