8x8’s anecdote provides a good point to make the distinction between ejaculation and orgasm. Both can be had independently of each other, and both have different effects on the penis. Ejaculation is merely the release of fluids, which as many people who edge can probably attest to, if you get too close to the edge and hover there at the point of no return then you penis can pump and release fluids as if you were ejaculating from orgasm. However, the feeling is significantly different and often the erection can be maintained and so can the need to “cum.” orgasm is much more physiologically and psychologically involved, as orgasm stems from the release of hormones and changes your body chemistry briefly. The release of several different neurotransmitters has a huge a effect on smooth tissue contraction. This area of neurobiology is receiving more attention (because sex is pretty friggin important), but is surprisingly bereft of solid research. Whether cumming is good or bad for PEing is completely personal, and you just gotta do what feels and works best for you. However, most of the evidence that I’ve seen suggests that edging and not cumming while masturbating will aid penile growth and EQ.
Personally, my EQ is so much better when I PE and edge, and save up my orgasm for when I’m enjoying the company of my lady friend, that I don’t even feel a strong need to cum while masturbating. It just makes me more excited for the next time we are together.