For me it's a matter of risk vs reward. An experienced receiver who you hook up with specifically for that purpose is going to consistently enjoy it. The receiver enjoying it is always my goal (I'm not into the S&M side of enemas), so I loved doing this.
However, the greatest experience I ever had giving was to an inexperienced former GF. She was the first I ever opened up to about enemas (we were in our mid-20s), and I was able to finally do so because she was very open minded. Though she'd taken anal sex off the table because she'd tried it with a former BF (reportedly smaller than me) and found it extremely painful, she'd been open to and enjoyed a finger in her ass when I went down on her, and she'd returned the favor. Long story short, I screwed up the courage to tell her I sometimes took enemas and had fantasized about the two of us giving each other enemas and me douching her. As I expected, she had a "sure, I'll try anything once" type of response.
When she next visited (at that point we were in a long distance relationship), I had everything ready, including two new douche/enema bags for her front and rear. Though I'd probably go right to coupling the enema with clit play if I had it to do over again, I kept her first enema pretty much clinical. Afterwards she was all smiles and said it felt "interesting" and felt really cleaned out, which felt good. While that reaction was very good, the most erotic experience of my life was the next day when I gave her a douche and enema at the same time while she played with her clit. The sounds she made were so exotic, and I could tell that her orgasm was almost overwhelming. After she relieved herself she confirmed it was by far the most intense orgasm she'd ever had and that she was all for future enema play.
That response when I had no idea how it would turn out was a grand slam home run. However...
The only other enema virgin I deflowered was my wife, and it did not go nearly so well. She has a complete hang up on just about all things anal, and she is mortified that I am even aware she poops. She thought of enemas only as something one might use as a last resort for terribly uncomfortable constipation. Though she did not freak out when I told her about my enemas (I first told her I took them for medical reasons - which was/is true - before sharing that I found them erotic) and eventually gave them to me (and at this point gives them to me weekly with a fantastic blow job), I was unable to convince her to try them for minor constipation nor purely for sexual stimulation.
She finally agreed to try it only whe she was severely constipated, and she was convinced before we started that it was going to be a horrible, painful experience. Because she expected that, it, of course was. I went slow, I did everything I could to comfort and sooth her, but there was just no way her mind was going to let her perceive the experience as anything but awful. Though I used the small standard enema nozzle, lubed both it and her well, and massaged her back passage externally in a futile attempt to relax it/her, she found the nozzle very painful. As soon as she heard the click of the clamp release she started panicking (even though I had the flow rate at a trickle). She was just absolutely convinced she was going to lose all control and shit all over me and our bed, and then she'd never be able to face me again. When she begged me, crying, to stop, she'd probably only taken about 6-8 ounces of water, and she was unwilling to try to hold even that. Not surprisingly, this did nothing to relieve her constipation, and it certainly did nothing for her sexually.
While she's loosened up a *little* about enemas for her (she let me give her a bulb once and a disposable once when she was very constipated, and she regularly uses the enema function on our bidet to take just a little water in complete privacy), I do not believe she'll ever find them erotic or even neutral.
That said, she's an excellent giver, she enjoys making me feel great every week, and she has done so for about 20 years now. So on the whole I consider myself quite fortunate.
So I had wildly different experiences with my two first time enema recipient's - the highest of highs and the lowest of lows. I also feel like I have to factor in the other potential negative outcome of introducing someone to enemas, and that is refusing to even give it a whirl. That happened to me twice, ending both relationships. When I factor that in I land squarely on a preference for giving to an experienced woman. Luckily, I had that experience a few times (via internet hookups) in the time between breaking up with the first lady I mentioned and meeting my wife.